Can't help with the serial number, but I've successfully made a few lensboards for my Anniversary.
I've put up a webpage that describes the process I used (probably a lot more stuff than you wanted to know). The lensboards aren't particularly odd, but they do have a beveled edge on the bottom. Otherwise they're just a 4" square piece of whatever (wood, mostly), about 1/8" thick or so.
I think lensboards can still be purchased but they're "relatively" expensive--I seem to recall prices in the $15-on-up range. A hunk of basswood sufficient for 4 lensboards is $2. Obviously there's the question of time and tools as well, so whatever's easiest for you.