Lark is a brand name associated with a company that specialized in luggage or
portable locks. Many such companies produced keys and locks like these in the
1950s through the 1980s.
These keys likely go to Lark-branded luggage or lockable travel cases. They
could have been used for anything from hard-sided suitcases to briefcases,
document boxes, or even certain types of security boxes designed for personal
travel. The small size of the key suggests that the lock it opens was not
designed for high-security purposes but rather for basic privacy and deterrence
of casual tampering.
They likely belong to a warded lock.