Thomas Trigger
Michael,
A very little on the Thomas trigger.
AR August 1938, In a dopebag article, "Special Triggers" The Thomas trigger is mentioned in about 3 paragraphs, but nothing on adjustment.
Also, in the June, 1941 issue of AR, page 51 he has an ad. At that time it cost $15.00. Not cheap in 1941.
I do not have a Thomas for a 37, but do have one for a 52B. Unfortunately the triggers are made quite differently. Where yours appears of laminated design, later triggers for the 52 are a solid block. However possibly one common link is that the adjustments are numbered and possibly the numbering system is common to the particular adjustments. I will dig mine out and get back to you.
One thing to remember is that though these are fine triggers they were designed for 3lb use with little variation.
Its hard to correctly "date" a target rifle because other than factory, few were assembled complete at the same time. They seemed to be done in stages over a period of time either as money allowed or "up grade" was felt necessary.
bjm