I have one of those in the white, 1.5" with slip fittings. Not sure if the grey is schedule 80, but if so there is no reason for that over the schedule 40 except for pretties i guess.
I didn't try to see if its able to be disassembled, it looks like it should be, but it may have been bonded at the line... Not that i planned to maintain it anyway, a 1.5" valve is unlikely to find anything that can block it in my tank. Adjustment is smooth enough and precise enough that unless something else goes wrong (like ATO being empty for a day without noticing =C) it is perfectly stable.