How to get a serial number??

[Marlexy]

Hi everyone

I bought a Rolex from my cousin, that watch belong to my beloved aunt who passed two years ago. The watch was stolen from my apt in USA, with the watch the thift got the repaired receipt that was the only information I had about the watch serial.

I just got the number under the six 568, ti was made on May 1968, the business where it was repaired in Venezuela is closed and I have not found a way to get the serial number to give it to the insurance company.
I didn't do a purchase document, which would be done if we have the serial.
My question to this Forum, is there a way to get the serial number? Any ideas?

Thank so much,

Malexy