Commemoratives do have collector interest, but it is quite limited. For the most part, a Tennessee police gun has little interest outside that state. S&W made a lot of such guns. They were usually ordered for members of a specific agency and laser engraved accordingly. They would be sold to department members to raise funds for a charitable organization, like a police benevolent association.
It may be an exception, but I checked the Blue Book for one such, the Georgia State Patrol commemorative. It is a Model 26-1, with 800 made, and the price given is $1350. But a standard Model 26, new in the box, is listed at $4500. So much for commemoratives as investments!