Post a picture and many should be able to help you out. Skeet / Trap etc. may be based off the comb height, offset, stock etc. There is several options to help you distinguish. Also in many cases it may be stamped on the side of the receiver. You may have a 870 Wingmaster set up for Skeet? Or a plane jane 870 Wingmaster. You can also buy a gun blue book and look through it.