Error: PE should be FP, sorry.
The FP appears to be a logo. It has a oval circle around it and a line
between the F and the P. It is made of plastic. I have read that the
Marelon are not bad seacock and are a plastic of sorts, could this be
an earlier model? The boat was launched 2000. There are 3 of these and
they all appear to be working perfectly. I also found:
50-11/2
DN-40
written on it.

The boat is steel. Would a bronze fitting not cause electrolysis? What
would be the best type/brand to use here (without going overboard)?

Currently: There is short piece of steel pipe welded to the opening in
the hull and threaded at the other end. The existing seacock is
attached to this. A replacement that screws onto this would be easiest
to install. Any recommendations?

And No, it not *riveted* in place. What I think you see as rivets are
bots which hold the seacock together, not in place.