The oldest dated bow I have by Gilman is 1936. I have a couple that are signed, with a velvet like grip covering, but they are undated and appear to be examples of his earlier work.
I have never seen one of his bows with an arrow rest - he believed in shooting off the hand. It may be a later addition, or he may have custom made some for the school. Gilman used bone/horn for his arrow strikes. I own the punch he custom built to outline the area on the bow that he needed to inlet for the standard sized inserts he made. I also have a few of the inserts.
The growth ring density on his bows varies quite a bit. Some are so close they are hard to see without magnification, others have only a dozen or so rings. It is interesting that, on some of his bows - especially the earlier ones, that the heartwood actually covers a bit of the back on the rounded part of the edges. He cut most of his wood in the High Cascades - he didn't like the lower elevation wood, the growth rings are too thick.
Most, if not all, of his bows are spliced in the handle. He made a special fixture for his huge bandsaw to cut the splices quickly and precisely.
I asked Gilman about shooting those brittle 50-60 year old bows. He said they were made for shooting - if the bow broke, get another one.
I have shot the 60s bow about a decade ago. I exercised it quite a bit over a couple of weeks before I finally pulled it to full draw - listening carefully for cracking/popping sounds and examining it carefully for compression problems. I then exercised it at full draw about 50 times before starting to shoot arrows. It may not have helped, but I have seen old bows blow up when yanked to full draw without warming them up - even fairly recent yew bows.
At last count, I have over 50 longbows in my collection, so of them I made myself.
Bill