If you've tried a 48DP pinion and the teeth are too widely spaced to engage with the spur on your FTX, then you have a 64DP spur. If the number of teeth on your spur are in the range 88 to 100 teeth, the you have 64DP; if it's 66 to 75 then they are 48DP.
That should be enough for you to identify which DP you have, but if not come back to me and we'll try some other clues! HTH
