The checklist below may be helpful in guiding your research on your church windows.
1. If the date of the window is known, check old invoices in church records.
2. Many windows were done as memorials, so check the church’s book/log/files for memorials.
3. There was probably a dedication service, and if you know the dates of installation, you can check old church bulletins.
4. There may be a published history of the individual church.
5. The windows may have been done in conjunction with major sanctuary renovations. This would be documented in church files, either in the church office, or building committee files. There may also be information in trustee records and/or session minutes.
6. Older individual church records may have been archived with the church’s denominational headquarters (e.g., Methodist regional conferences, Catholic dioceses, etc.)
7. Local or regional historical societies, town historians, and the public library may have compiled information from newspaper clippings about the church. If the donor of the windows is known, an obituary might hold a clue. Preservation organizations may also have information.
8. Sometimes, there are small signatures in corners of windows or logos. Dates can be included in memorial inscriptions.
9. Knowledgeable stained glass historians, ornamental glass experts, and conservators use the appearance and construction of the window’s details to help in identifying period of manufacturer, and possible firm:
10. A local stained glass studio may also be able to assist, because the artists might be familiar with similar windows in the area.
11. You may find articles or advertisements related to your firm in historic newspaper databases. Some of these are free to search online, such as the Library of Congress's Chronicling America. The state or country where your firm existed may also have digital newspapers online. Try looking at Elephind, which collects together numerous digital newspaper databases or search your country/province/state name for digitized newspaper projects.
Note: Points 8-10 appeared on the listserv H-Stained-Glass@h-net.msu.edu, contributed by Roy Coomber and Neal Vogel, 16 August 2009.
The checklist should serve as a good starting point for your research if you have not already exhausted the mentioned possibilities.
Books
Articles
Websites