Strut, my guess is that someone removed the grill assembly from your amp and covered it with cloth, then reinstalled (and perhaps even decorated it). The grill material that Valco used was a steel (they have been known to rust and 'pop' the flocking) screen, stapled to the plywood. Rather than remove this, most people left it alone and recovered it in the way mentioned above. I have seen a lot of Valco/ Gretsch amps like this over the years. Same goes for the amp covering. I remember bidding on Paul's amp along with him and we were bidding on a 'white' amp. After he got it - he removed the white material to find the original covering in really nice shape!
The flocked screening is currently not available for that amp.
However, they can be re-flocked..
Is the piping missing altogether or just dirty? It should be yellow.