Hydraulic pumps.... by Maximator
some claimed that theirs was stamped MO22 511
which matches up with a model from maximator.. Obviously they would have to be cleaned, but I would be concerned with safety since pumps designed for liquid service dont have to be made to as exacting specifications as a gas pump... (and are usualy alot cheaper)
http://www.maximator.de/
at 4.5lg its a bit heaver than the others..
1.28:1 stoke ratio, 9.2cm3 per stroke, 3.9lpm at 10 bar (seems a bit slow, gas should be a bit faster)