I find that things go in waves—this is the second old wooden drafting triangle I’ve found in as many weeks, perhaps because finding the first reminded me what satisfying things these are, so I’ve had an eye out. And this is really a pretty one--the wood is lovely and in great shape, with many many years of precise line drawing left in it.
Lengths of the sides are: 12 1/2”, 10 7/8” and 6 1/2”. A couple of old black ink stains as pictured, which in this case I think just enhance it.