Meltrope 2 with different patent numbers ?

[poodling around]

I am probably barking up the wrong tree here for a change .......... I just wondered about this.

In a nut-shell I saw an ebay item yesterday:

https://www.ebay.co.uk/itm/236688085494 ... R9L_3ZWeZw

and noticed that it seems to have a Meltrope 2 sound-box ?

However, comparing it to one or two which have sold on ebay it seems to have slightly different prov. pat. numbers ? They are difficult to read ('magnified' photo 'below') - but it seems so ?

I can't access the two or three I have at the moment to compare those.

So I wonder, are the numbers different and is this unusual ?

Thanks for any help as always.