Thanks, Steve. I knew the D series, but couldn't place the D4. They got a lot of mileage out of that rather simple action. It is basically the same as the Unique .22 I have that was sold by Sears back in the 1950's. I am sure the target versions had improved trigger pulls, but it is the same action. Unique also made the DES series which were really nice match pistols. A friend had one in .32 S&W Long that I fired a bit and it was extremely accurate. They were sold here in both .32 and .22, but the .32 was never able to break into the American center fire match market which the .38 Special had locked up.
I would put the retail value in top condition in the $450 range, but others may have a better idea.
Jim