Photo Log ??

[Joankraig]

A while ago my husband and I began a relationship with a 'cuckold dom'. So far, while we have pushed a lot of boundaries, we have found this to be very erotic. At the start, it was agreed there would be no pictures with the exception of one, non-identifying photo that was taken last week. It showed only my hand on his cock immediately after he had cum with his cum running down my (left) hand and his cock. He wanted (and we were fine with) a photo of his cock and cum over my engagement and wedding ring. On Friday he showed us, what he called "his log book". An album with about a dozen similar pictures - his cock and cum with different hands and rings. Some of the rings appeared expensive and others were a simple gold band. He told us that this was his log to document the couples he has been with. There were no names or dates. He said it was a way for him to recall the couples he has been with. My question is, is this a common thing for a cuckold dom (or any dom for that matter) to do? I am more curious than anything else.