Hey Weldman,
I'm currently in the middle of a restoration of my 276. I've not been able to find anything on dating the serial numbers (but I have considered contacting Wayne and seeing if they happen to have any 90 year old records lying around...).
There are a couple of ways to date it to an early one or late, as there were subtle differences in pictures I've seen and ads/catalogs I have that can help date it a bit. DB on the board here has had one for years and help put me on the the subtle (and not so subtle) differences. He would be good to talk to as well.
If you want to trade stories as we work on them, send me a PM and I'll give you my email, or check out my pictures and progress reports I'm posing on my Facebook page:
http://www.facebook.com/topic.php?topic=202&post=604&uid=172022916180049#!/topic.php?uid=172022916180049&topic=202.
I'll post major updates on the forum here, but don't want to bore everybody with picture after picture of rusty metal
I've got my tore down (not easy to take these apart, and HEAVY) and half sand blasted, but it's on pause while I finish a Wayne 615 for my Dad.
By the way - the serial number on mine is 159590
