Know what this is?

The B-29 used Jack Screws for opening the bombay doors

The B-50 had air operated bombay doors

This may be from a B-50

Dick

TB-50A - TB50D - TB-50H Flight Engineer

The jackscrews were changed to pneumatic actuators early on to speed up retraction and opening. When opening bomb bay doors on the ground a safety pin was installed to prevent accidental closing. They closed so fast that it was said that it could cut you in half. I don't know about that, but it would have probably of killed or injured you awfully bad.

I wonder if there is a way to see if the aircraft that this thing came out of is still in existence from the serial #'s on the compressor????

Yes I got two of them a few years ago.  I was told they were also used for gun operation.  They can do 1800 psi and many got them to fill SCUBA tanks.  I started to do that but never finish the project.  You have to use an oil that is OK to your system when the oil vapor is in the air you breath or you can have problems with your lungs getting a bit of oil which can cause breathing problems as you might understand.  Jerry in MN

Ken: The only time you could really be sure what a/c it came from, is right after DD-250, transferring the a/c to DOD. The DD-250 paperwork will contain a listing of every serialized part on the a/c at that point. I've had to deliver a/c where we changed serialized parts post DD-250, and it's a paperwork hassle. Trying to track what was on a delivered a/c, from records that are more than 15 years old, is almost impossible. Repairs, failures, upgrades and the like, all complicate the recordkeeping on the individual a/c.

With the little fan on the front it sorta  looks like a primitve ( RAT ) Ram air turbine  that was thrust into the airstream to proivide auxiliary hydraulic pressure in the event of a emergency.

The little fan blade actually doesn't look substantial enough to me to do much more than move cooling air over the fins of the compressor heads.