Need info about ex-police 870 Wingmaster

[Kiwigunguy]

I've got an ex-police Wingmaster that I need help identifying. It's a 1973 production model, and is fitted with a Choate pistol grip stock and forend. It is marked S · 60 on the left side of the receiver above the trigger guard, and SCSD C (possibly Suffolk County Sheriff's Department?) on both sides of the stock near the buttpad. There are other Wingmasters set up the same way, some marked SCSD on the receiver. Does anyone have any information or photos of these 870s?