If those are ABN, which are stock TT .36 stuff, the base metal is brass, so the cylinder will be quite heavy. If they're light, they're aluminum. When brass cylinders are NICKLE plated, all surfaces are NICKLE plated, including OD and the ports, flange, etc. If they're chromed (either aluminum or brass), the base metal will be bare in the ports, on the OD and flange. If you determine that the plating is all over, you could file away a bit of nickle on the edge of the flange a bit and strike brass, without damaging the cylinder. I am not sure if there is a market for stock TT .36 cylinders without pistons.
My guess is that they're stock cylinders, because if they were chromed aluminum (Randy Aero) parts, the pistons would be fitted to each specific cylinder. The only other (slim) possibility I can think of is that they're really Brodak .40 cylinders, which don't (or didn't) come with matched pistons...which is absolutely not a good practice IMO.

Steve