The person of interest is Solomon Sherevsky.
It is recorded that he had 'five-manifold'  synesthesia that allowed him to do several above average capabilities(some even break the limit of what I think NH can do, while some we can alreay did it).
The capabilities were:
1) can memorize things in details. as long as he had given sufficient time to use his special synesthesia, usually only several minutes.
2) the memory can be recalled again a century later in details.
3) the memory can be used to change his heartbeat up and down, which can suggest that he has probably more than 'five-manifold' synesthesia.
4) the synesthesia structure when he looking a number was an anthropomorphization with personality. This could suggest that he was using metaphor because one of the hallmark of metaphor is using character or role.

However, it is recorded that he cannot differentiate between real memory and metaphorical memory, because to him, all seems real. so what do you think, is it just overused low-level synesthesia?