How to identify HP-49g+ production runs

[Giancarlo]

Hello,
i may be wrong but if i remember correctly the first HP49G+ units had a lot of troubles with the keyboard. Keys were too hard to press and often you entered more digits than required.

HP replaced the faulty units and then i got a new version.
I still like it a lot. If i don't have my Prime around, my second choice is the HP49g+

Thanks

Giancarlo