50g - Differences in production batches

[Marco Polo]

Some time ago I got a spare HP50g unit.
My workhorse is a 50g I got in mid 2007 as warranty replacement of my 49g+.
The spare unit came without box/blister, but with canvas pouch. I presume it is more recent than my workhorse.
Examining the two units I noted some differences (see photos)
1) the "bezel" of the spare unit is not as smooth as the other. Furthermore it seems to have some "glitter" in the mould
2) the words painted on the spare unit are ticker
3) the certifications on the back are different, with a reference to a HP49G+(2) on the spare unit
4) the battery compartment is identical, but in the spare unit some wires are visible through the apertures

Anybody can help to understand when the spare unit was produced and if there is any further hidden differences?

Thanks