Is there a known way to date GT31s by their serial numbers?
Most of mine begin with 11 or 13 but now I have one that starts 83
I bought mine about 09. The SN is almost erased but it looks like it starts 932
So is the year the start? That could make mine march 09? Be about right. I'll see if I can confirm when I bought it.
Looks like I bought it early 2010, but it could have been made a year earlier I guess.
If so your 83 would be one of the first made I think. They certainly weren't around a year before that.
The last purchase of GT-31's I got was in 2013. The serials are consecutive on these two. 1332010** make of that what you will. 
I will have a look around for my older ones......
