So, I finally bolt modded my 1390131. I knew that it needed doing as soon as I got the board- I could hear the rattle of broken rivets when I picked up the board for the first time. Sure enough, when I opened up the board there were quite a few broken rivets rolling around.
Here's a few pics:
Need to rehost, sorry
I made a couple of mistakes (drilled a couple of holes wonky, put two bolts in numpad area where they get in the way of stabilisers) but nothing I couldn't fix. Not bad for my first try I guess.
I followed the rather excellent guide here:
http://geekhack.org/showwiki.php?title=Island:12093Overall I'm really happy with the results- the board feels amazingly crisp and solid, and the buckling spring switches feel much snappier. I'm keen do bolt mod my other Model M now (although it doesn't really need it- I checked it the other day and it doesn't look to have any broken rivets at all).
A couple of points about my 1390131:
-It's ANSI, but made in the UK. I thought this was a bit strange- is this sort of combo common?
-Side by side with my white label M, the casing on the 1390131 looks to be a slightly lighter shade of grey. I guess this is normal?
-Is it true that Silver label M's are more rare than others? I guess they are some of the oldest around?