I appreciate your effort, but unfortunately it does not help. Yes, it most likely is a Futaba receiver rebranded. But searching this incredible place I have found some of the IC:s and the 455KHz quartz filter. The 31136G is used both for single and dual conversion but it should be one more IF quartz filter I think. So my guess so far is that it is a single conversion receiver wich will give the crystal to be used. The decoder IC I still have to find out but the cheapest guess is PPM.