What are Model 41 barrel weights worth?

If you are talking about the Screw in Weights, in the end of the 7 3/8 barrel, usually $15-$25.00 ea.
The Olyimpic Counter Weights are another story.

The external weight sets can run $300 or more depending on condition and if original box is present. There are a couple of variations of markings and number of screws to attach the bottom two weights....two screws vs four screws. Most external sets are all steel but supposedly they made all aluminum sets also but I've never seen a set. The following shows a steel set on the left with aluminum upper weight on the right. Steel and aluminum internal weights are at the bottom.





Witness mark on the barrel.