campy seatpost ID help
 

It's fluted, single allen bolt, and has a dark grey head with a distinctly rough/pebbly finish. What is it?

Without a picture, I'll guess Super Record.

I would also guess Super Record but the allen head bolt doesn't belong to the SR seat post. Cinelli supplied a replacement allen headed bolt with their VIP set to accomodate the wider rails of the saddle that came with the set. The bolt was aluminium alloy though.
The bolt head, being quite narrow, can be rounded off easily and an obvious replacement would be an allen headed bolt.