Thanks for posting the pictures. Very nice!
There has been several different labels over the years and also different signatures. I will add some pictures for you shortly of the labels that I have in my collection.
Does B stand for fish? I would say no! I have some examples for you:
B6, B7 polarbear
B15, B16, B100, B101, B645, B673 fish
B87, B105, B155 bird
B746, B747 Snoopy
B774, B775 whale
There are lots of different pieces but I can't see any pattern here with the numbering! I guess there is a reason for different numbering but it's not that obvious. Has it got something to do with the size or colour variations? I don't know!
I have for instance seen the pear (gold) = with label only, with signature only, with label and signature.
The next numbers usually indicates the size. The signature on your fish looks like B850 and then possibly 100. Which would then indicate the size 100mm = 10cm. Is your fish approx. 10cm?
I don't know how often they changed labels but I would date your gold/black label early 70's (possibly late 60's?) and the silver/black one mid or late 70's. My owl has no signature but the gold/black label.
I'm certainly no expert here so I welcome all the information that I can get!