About how old would it be?
@$900 with whip and filter seems too good to be true
Like with a woman I don't know which of two questions would be harder to answer.
Guessing her weight or her age.
If I was pushed 25 years +/- and light enough to lift with one hand would be my answer being the gentleman that I am.
The key observation would be on the 3rd stage head of which 3 variants were made on the SA-3E
1st was Aluminium Black anodised and plain machined with no central 1/4NPT blank plug on the back so to remove the internal valve assembly and reeds you had to pull the valve out using a 6/32 bolt attached into the valve body.
The 2nd variant was change to stainless steel (non magnetic) same size and thread fittings 1/4 and 1/8 NPT for the inlet and outlet as the earlier aluminium head but in stainless to ensure a longer head body life
The 3rd and later variant was also in stainless but with a 7/16 UNF plug fitted centre back that enabled you to push the entire valve assembly out using a drift or dowel from the back end.
The dowel diameter had to be smaller than the reed valve centre hole to avoid bending the reed valve when pushing it out
The valve itself was also redesigned changing the material from a hardened steel again to a non magnetic stainless.
The other change was on the 3rd stage cooling coil changed from 1/4" half hard copper
to 3/16" stainless steel but with the additional change of using a 37 degree flared tube end fitting known as a SAE JIC flared end fitting. Great for the military customers and our workshop but not so favourable with individual scuba divers making up flared end fittings and contemplating copper crush seal washers during service.
All sound engineering 101 but hard to transfer the workshop skills with the fittings change. Iain
Iain