Vintage 1975 Unusual Artist Signed Sterling Silver Fish Brooch Signed & Numbered

Vintage 1975 Unusual Artist Signed Sterling Silver Fish Brooch Signed & Numbered

Here is an unusual fish brooch
It is sterling silver
The brooch is artist signed but I can''t make out the electric pen signature - looks to me like D. Tw???
It is dated what looks like ''75 under the signature
The brooch is also numbered what looks like 4/50