Zero. No Turing machine has ever been built. The tape needs to be infinite to be a Turing machine.
I've found "self-interpreter" implementations that aim to be short
https://arxiv.org/html/cs/0311032
https://codegolf.stackexchange.com/questions/585/self-interp...
But I haven't found anyone yet that optimized for actual number of recursive implementations on a real machine.