How to tell a bidder was converted to a supplier

Is there a table that shows that a supplier was converted from a bidder?

We have found the AUC_BIDDER_XREF table, although, it seems to populate both "Bidders" that were never set up as a bidder as well as bidders that created accounts through the supplier portal.

We just want to see actual bidders created using the supplier portal, that were actually converted to a supplier.