The Callaghan-class police cutter was not a unit of Star Fleet, but was a law enforcement ship designed to protect and service the citizens of the Federation (and enforce the laws including customs and tariff enforcement). During wartime, many police ships were "drafted" into Star Fleet and used as small frigates (over the vociferous objections of the Police Commissioner).
The ships of the Starline 2500 series are cast in pewter, have supremely high detail, and are in a larger (1/3200) scale than the earlier, metal 2400 series of miniatures. The ships of either series will work with Star Fleet Battles, Federation Commander, A Call to Arms, or Starmada.
This product is being done as a joint venture with Mongoose Publishing Ltd., under the strict terms of ADB, Inc.'s contract with Paramount Pictures Corporation.