That is a great price, if it is not infected with fungus or separation. It is a very good lens, but massive. I don't have a Canon 1.2, but the 0,95 improves quickly when stopping down.
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Leave it to the collectors, the ONLY point of buying such a fast lens is to use it at these apertures. This is what I did in the late 70's for Astrophotography, photographing meteor trails against star fields. Its aberations, mainly coma, made it next to useless for the purpose.
I sold mine for double what I paid for it, and later bought the far better f1.4.
A friends f1.2 was not much use either.
Bizarrely the acknowleged best lens for the astro purpose in the meteor section of the BAA at the time was the Russian Helios 58mm f2!! It gave a flat sharp field wide open. There was the odd dud, but in the main they were excellent.
I sold my f.0.95 and the Canon Mirror Box, to a "collector" for a sum which later bought me a brand new Pentax LX with a fancy finder system and a f1.2 Pentax lens.😉