Just opened my knife drawer here in Oman where I work and saw the Cuttlefish bone. The reason it is there is it is an excellent "strop" for a blade. (A South African mate told me about this. I tried it and it works)
One side (the harder side) is good for turning back any burr, the other is superb for honing a fine edge. Be warned that it is very messy as calcium will get all over the place.
Any-one living near the coast (anywhere) should easily some washed up. If further inland try a pet shop. Caged birds eat 'em and reptiles (tortoises especially) love 'em. (pet shop cuttlefish may not have the coarser side though)
Just thought I'd share
From hard won experience.... Never, ever, let the misses use your blades unless she is "dishwasher proof". In order to prevent my wife using my blades (in England) for peeling spuds and opening boil in the bag rubbish, I know keep them in the safe,.. Cant take any chances
High carbon steel and salty dishwasher tablets are a bad combination.
"I only go fishing religiously every week end to make amends for all the fun I have in the office during the week"