I'm a hvac/r tech. Usually when a leak detector is going crazy in a fridge like that it is leaks in the evaporator coil (inside coil). Did he only detect leaks inside, or at the compressor below as well? What you do next will probably depend on where your leaks are.
As for the r12 thing, r22...
Some stuff I don't need.
Snap On timing and advance light MT-241 has owners initials. $50 shipped in the USA.
Balkamp 700-1115 Cooling System test pump/gauge. Has owners initials. $40 Shipped in the USA.
Don't know much about this box from an old service station. Measures 21.5"L x 8.5"W x 7.5"H, has copyright date 1963 on it. I've never seen another one like it so it must be pretty uncommon. $75 shipped anywhere in U.S.A
Small Tire patch in a can. 1950's maybe? Has contents, I've...
I've been toying with the idea of making my next tool box bench top as follows:
cut to size and laminate 2 pieces of 3/4" plywood together
spray the whole top and sides with spray adhesive
cover with thick cow rawhide
oil
I did the math and it would actually be less than most block tops, really...