Bought a used Daisy Powerline 747 (0.177") pellet pistol. It would not hold air, and the price reflected that issue. Three o-rings from the local general store for 48 cents/each restored compression.

This one is bit of a Frankenstein. It has a metal adjustable rear sight ( supposed to be plastic), and a walnut anatomical grip (should be slimmer plastic version with thumbrest). Looks like those two parts came from the premium Daisy Power line 777 model. It does have the steel Lothar Walther rifled barrel, and a trigger adjustable for weight.

Accurate little fellow. Anyone else have one? What pellet design/weight/make does it prefer?

This is your guy...B. B. Pelletier...

https://www.pyramydair.com/blog/2005/11/daisy-avanti-747-the-perfect-indoor-target-pistol/

I played with the cheaper version 717 (not a LW barrel) and it was still pretty durn accurate. Heavy, and low velocity (~300ish IIRC). I was shooting H&N Lightweights Match pellets (High Speeds, I think they were 7gr). ...I lusted after a 747 or a 777, then my friend put his Pardini into my hands and it was all over! I believe the 747's came with wood non-adjustable grips with a knob on the bottom, and the 777's came with wood grips with an adjustable palm shelf.

How quite is that pistol?

Quiet. Just a soft "spit."