An (Irvin) APEX tie, it is the strap that connects the top of the chute to the rip cord. This one was a souvenir from a UK training jump of a 1st Can Para member in WWII. It is approximately 8" long.
I have a second one that was taken as a souvenir from the Rhine jump as well from the same 1st Can Para vet. I can't find the pics right now but will take some this afternoon.