Iconic. That's the Parker "51". This dove gray pen with a Vacumatic filler and stacked coins cap is a marvelous example of why the Parker "51" was and is so popular.
As is somewhat typical of this color there is a bit of staining. The barrel end has a faint ring from the clutch ring inside the cap and the shell (grip section) is faintly discolored from ink. Both are visible in the photos.
The nib is fine, wet and smooth. A design feature of the Parker "51" is to write immediately even if it has lain uncapped on the desk for hours. Perhaps not something you want to do often, but it is a desirable characteristic in a pen that can be carried and used every day.
I’ve disassembled the pen, replaced the Vacumatic diaphragm, cleaned the collector, reassembled and adjusted everything to be just so. I guarantee my work for at least 1 year provided you strictly avoid catfish ink. That stuff will eat the diaphragm.