This is part of Win16 API which allow to create versions of program from one source code to run under OS/2 and Win16. Under OS/2 program can be running under Win-OS/2 if program is Windows NE executable, and with help on Windows Libraries for OS/2, if it is OS/2 NE executable. Here is a WLO to OS/2 API mapping draft
Decrements the lock count of a local memory object.
BOOL WINAPI LocalUnlock( HLOCAL hMem );
hMem – Handle to the memory object.
Returns FALSE (0) if the lock count becomes zero (object is now unlocked).
Returns TRUE (non‑zero) if the lock count is still greater than zero after decrementing.
The return value indicates the new lock state, not success or failure – the function always succeeds for a valid handle.
Unlocking allows the heap manager to move or discard the block during compaction.
BOOL stillLocked = LocalUnlock(hMem);
push hMem call LocalUnlock test ax, ax ; zero if completely unlocked