You are describing the L-Comp.
Originally made for Camfour, these might be available (now) through other distributors, not sure.
As for value, tough question. There are regional variations on all these, but the biggest driver will be the vintage. This gun was originally made pre-lock, but it has also been made with the lock. The pre-lock guns will carry a higher value due to popularity (or lack of popularity of the lock version).
Here's an early one without the "IL".