I have 6 SEAs that I still use. 2 have the environmental (silicon top). 4 are DIN. 2 are yoke.
Great regs as they use the same internals as the rest of conshelfs, except the bottom plug o-ring which is 11x2 metric.
Took me a while to figure that out as the USD manual doesn't tell you. I bought a pack of 20 viton from a specialist supplier in the UK so I have spares.
The nice thing about the SEA is that it has four LP (1 1/2 and 3 3/8) and 2 HP - one either side. That means you can do any hose configuration you like - even side-mount. The first 2 I bought from new in 1988 - the rest I have accumulated from eBay.
Various second stages - gone through a lot over the years as they get the dreaded plastic cracking problem around the inlet (I striped and threw two away today for that issue)
SEA first stage also known as the
-Aqualung Cousteau
-Spiro Supra
the later is very popular in Europe. Lots of them on German ebay