The dagger has arrived, no markings, flattened diamond in cross section. Double edged and still sharp. 'Hot pin' test of the handle revealed it is definately of animal origin.....but what animal

Two indentations 180 degrees apart, on the 'shoulder' section as the blade meets hilt seem 'unusual' ...I've no idea why they are there
Without doubt this is a stabbing weapon, the blade is approx. 7mm thick (central ridge) and seems very 'robust' Patina suggests mid 19th C to early 20 th.
.... any suggestions to origin and use would be greatly appreciated...
Regards David