What I will do next is go to a refrigeration supply and see if I can match up a site glass as they are often used on commercial systems and are replaceable with seals. I purchased an HH off of ePay years ago not realizing there were variations of these while still marked HH! The one I got If my memory serves correct was from a Studebaker according to Vintage Air and they mentioned the site glass was horrible to find. As it ended up this mystery HH Techumseh was like brand new inside and I never had the heart to part it out. It has a much better design clutch than what the Mark uses with a magnet bolted to the compressor instead of the brush style. It is complete but suffered rust damage. If your seals are worn out you can probably ubtain some from the same type of supplier in your location.