How to re-align tailstock?

[rendoman]

Hi all!
I'm in trouble and ask for help, any advice welcome

I have an old lathe, the tailstock position is not correct and the centre is off axis.
There are some marks on the back of tailstock, the "0" seems out of phase, more 2 scratch to the side, maybe have been done later by hand.

Currently I got no double fixed point, no rectified bar, there is some way or tips for finding the correct alignement?

I take some picture

Thanks
Stefano