{"cik":"0002047235","entityType":"operating","sic":"6036","sicDescription":"Savings Institutions, Not Federally Chartered","ownerOrg":"02 Finance","insiderTransactionForOwnerExists":0,"insiderTransactionForIssuerExists":1,"name":"Winchester Bancorp, Inc./MD/","tickers":["WSBK"],"exchanges":["Nasdaq"],"ein":"000000000","lei":null,"description":"","website":"","investorWebsite":"","category":"Non-accelerated filer
Smaller reporting company
Emerging growth company","fiscalYearEnd":"0630","stateOfIncorporation":"MD","stateOfIncorporationDescription":"MD","addresses":{"mailing":{"street1":"661 MAIN STREET","street2":null,"city":"WINCHESTER","stateOrCountry":"MA","zipCode":"01890","stateOrCountryDescription":"MA","isForeignLocation":0,"foreignStateTerritory":null,"country":null,"countryCode":null},"business":{"street1":"661 MAIN STREET","street2":null,"city":"WINCHESTER","stateOrCountry":"MA","zipCode":"01890","stateOrCountryDescription":"MA","isForeignLocation":null,"foreignStateTerritory":null,"country":null,"countryCode":null}},"phone":"(781) 729-2130","flags":"","formerNames":[],"filings":{"recent":{"accessionNumber":["0001437749-26-018597","0001437749-26-018205","0001193125-26-221566","0001437749-26-015781","0001437749-26-015135","0001437749-26-014760","0001193125-26-191386","0001193125-26-046248","0001193125-26-027185","0001193125-25-279601","0001193125-25-277465","0001193125-25-246729","0001193125-25-236598","0001193125-25-236599","0001193125-25-206345","0001193125-25-206332","0000950170-25-100224","0001437749-25-019968","0001437749-25-017190","0001437749-25-016957","0000950170-25-071716","0000950170-25-069255","0001437749-25-015727","0001437749-25-014976","0001437749-25-014975","0001437749-25-014974","0000943374-25-000192","0001437749-25-014685","0001354457-25-000369","0001437749-25-013944","0001437749-25-013943","0001437749-25-013942","0001437749-25-013941","0001437749-25-013940","0001437749-25-013939","0001437749-25-013938","0001437749-25-013937","0001437749-25-013936","0001437749-25-013935","0001437749-25-013934","0001437749-25-013933","0000943374-25-000183","0000943374-25-000173","0000943374-25-000172","0000950170-25-045817","0001193125-25-060347","0001193125-25-058404","0001193125-25-058343","0001193125-25-031426","0001193125-25-028296","9999999995-25-000389","0000943374-25-000069","0000943374-25-000068","0001193125-25-021824","0001193125-25-014434","0001193125-25-014427","0000000000-25-000193","0001193125-24-276691"],"filingDate":["2026-05-27","2026-05-22","2026-05-13","2026-05-08","2026-05-06","2026-05-05","2026-04-29","2026-02-11","2026-01-28","2025-11-13","2025-11-12","2025-10-22","2025-10-10","2025-10-10","2025-09-17","2025-09-17","2025-07-30","2025-06-10","2025-05-15","2025-05-14","2025-05-14","2025-05-12","2025-05-09","2025-05-07","2025-05-07","2025-05-07","2025-05-06","2025-05-06","2025-05-01","2025-04-30","2025-04-30","2025-04-30","2025-04-30","2025-04-30","2025-04-30","2025-04-30","2025-04-30","2025-04-30","2025-04-30","2025-04-30","2025-04-30","2025-04-30","2025-04-30","2025-04-30","2025-03-27","2025-03-21","2025-03-20","2025-03-20","2025-02-21","2025-02-18","2025-02-11","2025-02-07","2025-02-07","2025-02-06","2025-01-28","2025-01-28","2025-01-08","2024-12-12"],"reportDate":["2026-05-26","2026-05-21","2026-03-31","2026-05-07","2026-05-05","2026-05-01","2026-04-29","2025-12-31","2026-01-28","2025-11-12","2025-09-30","2025-10-22","2025-11-12","2025-06-30","2025-09-17","2025-06-30","2025-07-30","2025-06-10","2025-05-14","2025-04-30","","2025-03-31","2025-05-07","2025-04-30","2025-04-30","2025-04-30","2025-04-30","2025-05-05","","2025-04-30","2025-04-30","2025-04-30","2025-04-30","2025-04-30","2025-04-30","2025-04-30","2025-04-30","2025-04-30","2025-04-30","2025-04-30","2025-04-30","","2025-04-30","2025-04-29","2024-12-31","2025-03-21","2025-03-20","","","2025-02-11","","","","","","","",""],"acceptanceDateTime":["2026-05-27T20:54:59.000Z","2026-05-22T15:58:46.000Z","2026-05-13T20:02:39.000Z","2026-05-08T14:06:23.000Z","2026-05-06T17:24:26.000Z","2026-05-05T13:37:45.000Z","2026-04-29T19:54:53.000Z","2026-02-11T19:26:00.000Z","2026-01-28T20:57:53.000Z","2025-11-13T17:52:25.000Z","2025-11-12T21:00:55.000Z","2025-10-22T19:57:06.000Z","2025-10-10T14:00:28.000Z","2025-10-10T14:00:06.000Z","2025-09-17T21:14:23.000Z","2025-09-17T21:09:10.000Z","2025-07-30T20:07:13.000Z","2025-06-10T19:44:20.000Z","2025-05-15T20:15:07.000Z","2025-05-14T23:10:07.000Z","2025-05-14T22:36:07.000Z","2025-05-12T20:18:42.000Z","2025-05-09T16:53:07.000Z","2025-05-07T14:29:22.000Z","2025-05-07T14:28:48.000Z","2025-05-07T14:28:00.000Z","2025-05-06T21:19:07.000Z","2025-05-06T16:24:18.000Z","2025-05-01T16:45:05.000Z","2025-04-30T22:17:26.000Z","2025-04-30T22:16:44.000Z","2025-04-30T22:16:11.000Z","2025-04-30T22:15:27.000Z","2025-04-30T22:14:45.000Z","2025-04-30T22:14:08.000Z","2025-04-30T22:13:17.000Z","2025-04-30T22:12:40.000Z","2025-04-30T22:12:01.000Z","2025-04-30T22:11:19.000Z","2025-04-30T22:10:37.000Z","2025-04-30T22:09:54.000Z","2025-04-30T21:10:09.000Z","2025-04-30T13:05:59.000Z","2025-04-30T13:04:48.000Z","2025-03-27T15:41:17.000Z","2025-03-21T21:15:57.000Z","2025-03-20T13:02:07.000Z","2025-03-20T12:01:00.000Z","2025-02-21T14:18:23.000Z","2025-02-18T15:07:46.000Z","2025-02-12T05:15:11.000Z","2025-02-07T19:00:42.000Z","2025-02-07T19:00:17.000Z","2025-02-06T21:35:16.000Z","2025-01-28T21:43:54.000Z","2025-01-28T21:42:17.000Z","2025-01-08T16:36:06.000Z","2024-12-12T19:04:54.000Z"],"act":["","","34","","","","34","34","34","34","34","34","34","34","34","34","34","","","","34","34","","","","","34","","34","","","","","","","","","","","","","34","34","34","34","34","34","33","33","34","33","","","33","","33","","33"],"form":["4","4","10-Q","4","4","4","8-K","10-Q","8-K","8-K","10-Q","8-K","DEF 14A","ARS","8-K","10-K","8-K","4","4","3","SCHEDULE 13D","10-Q","4","3","3","3","8-K","4","CERT","3","3","3","3","3","3","3","3","3","3","3","3","8-A12B","8-K","8-K","10-Q","8-K","8-K","424B3","424B3","8-K","EFFECT","CORRESP","CORRESP","S-1/A","CORRESP","S-1/A","UPLOAD","S-1"],"fileNumber":["","","001-42627","","","","001-42627","001-42627","001-42627","001-42627","001-42627","001-42627","001-42627","001-42627","001-42627","001-42627","001-42627","","","","005-95022","001-42627","","","","","001-42627","","001-42627","","","","","","","","","","","","","001-42627","333-283752","333-283752","333-283752","333-283752","333-283752","333-283752","333-283752","333-283752","333-283752","","","333-283752","","333-283752","333-283752","333-283752"],"filmNumber":["","","26973121","","","","26915438","26619987","26572363","251476896","251472384","251410036","251386629","251386626","251320969","251320926","251167054","","","","25947649","25935138","","","","","25918355","","25901321","","","","","","","","","","","","","25897403","25891319","25891306","25777443","25761546","25754656","25754546","25648714","25633206","25611726","","","25597923","","25564856","","241544227"],"items":["","","","","","","2.02,9.01","","2.02,9.01","5.07","","2.02,9.01","","","8.01,9.01","","2.02,9.01","","","","","","","","","","8.01,9.01","","","","","","","","","","","","","","","","2.02,9.01","8.01,9.01","","8.01,9.01","8.01,9.01","","","1.01,9.01",",,","","","","","","",""],"core_type":["4","4","XBRL","4","4","4","XBRL","XBRL","XBRL","XBRL","XBRL","XBRL","XBRL","ARS","XBRL","XBRL","XBRL","4","4","3","SCHEDULE 13D","XBRL","4","3","3","3","XBRL","4","CERT","3","3","3","3","3","3","3","3","3","3","3","3","8-A12B","XBRL","XBRL","XBRL","8-K","8-K","424B3","424B3","XBRL","EFFECT","CORRESP","CORRESP","S-1/A","CORRESP","S-1/A","LETTER","S-1"],"size":[4359,6638,21911705,6956,7767,5054,891439,21923585,890728,159025,18739393,1122379,7262251,5555404,148044,25831847,944972,4111,6831,3531,14569,18025259,20447,3478,3452,4720,225030,18887,121108,4105,3490,3441,3439,3330,3331,4021,3325,4018,4020,4007,3332,16237,161734,225169,15771367,17715,17925,16358,3839720,498223,1734,40652,4303,3946811,25728,4673247,50747,9176551],"isXBRL":[0,0,1,0,0,0,1,1,1,1,1,1,1,0,1,1,1,0,0,0,0,1,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,0,0,0,0,1,0,0,0,0,0,1,0,0],"isInlineXBRL":[0,0,1,0,0,0,1,1,1,1,1,1,1,0,1,1,1,0,0,0,0,1,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,0,0,0,0,1,0,0,0,0,0,1,0,0],"isXBRLNumeric":[0,0,1,0,0,0,0,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null,null],"primaryDocument":["xslF345X06/rdgdoc.xml","xslF345X06/rdgdoc.xml","wsbk-20260331.htm","xslF345X06/rdgdoc.xml","xslF345X06/rdgdoc.xml","xslF345X06/rdgdoc.xml","wsbk-20260429.htm","wsbk-20251231.htm","wsbk-20260128.htm","wsbk-20251112.htm","wsbk-20250930.htm","wsbk-20251022.htm","wsbk-20251009.htm","wsbk_ars_2025.pdf","wsbk-20250917.htm","wsbk-20250630.htm","wsbk-20250730.htm","xslF345X05/rdgdoc.xml","xslF345X05/rdgdoc.xml","xslF345X02/rdgdoc.xml","xslSCHEDULE_13D_X01/primary_doc.xml","wsbk-20250331.htm","xslF345X05/rdgdoc.xml","xslF345X02/rdgdoc.xml","xslF345X02/rdgdoc.xml","xslF345X02/rdgdoc.xml","form8k_043025.htm","xslF345X05/rdgdoc.xml","8A_Cert_WSBK.pdf","xslF345X02/rdgdoc.xml","xslF345X02/rdgdoc.xml","xslF345X02/rdgdoc.xml","xslF345X02/rdgdoc.xml","xslF345X02/rdgdoc.xml","xslF345X02/rdgdoc.xml","xslF345X02/rdgdoc.xml","xslF345X02/rdgdoc.xml","xslF345X02/rdgdoc.xml","xslF345X02/rdgdoc.xml","xslF345X02/rdgdoc.xml","xslF345X02/rdgdoc.xml","form8a_043025.htm","form8k_043025-earnings.htm","form8k_042925.htm","wsbk-20241231.htm","d918166d8k.htm","d902092d8k.htm","d879299d424b3.htm","d894037d424b3.htm","d925775d8k.htm","xslEFFECTX01/primary_doc.xml","filename1.htm","filename1.htm","d914289ds1a.htm","filename1.htm","d914289ds1a.htm","filename1.pdf","d914289ds1.htm"],"primaryDocDescription":["FORM 4","FORM 4","10-Q","FORM 4","FORM 4","FORM 4","8-K","10-Q","8-K","8-K","10-Q","8-K","DEF 14A","ARS","8-K","10-K","8-K","FORM 4","FORM 4","FORM 3","","10-Q","FORM 4","FORM 3","FORM 3","FORM 3","WINCHESTER BANCORP, INC. FORM 8-K APRIL 30, 2025","FORM 4","","FORM 3","FORM 3","FORM 3","FORM 3","FORM 3","FORM 3","FORM 3","FORM 3","FORM 3","FORM 3","FORM 3","FORM 3","WINCHESTER BANCORP, INC. FORM 8-A APRIL 30, 2025","WINCHESTER BANCORP, INC. FORM 8-K APRIL 30, 2025","WINCHESTER BANCORP, INC. FORM 8-K APRIL 29, 2025","10-Q","8-K","8-K","424B3","424B3","8-K","","","","S-1/A","","S-1/A","","S-1"]},"files":[]}}