The lock comprises a lock bolt, in particular a latch bolt (17), the actuating mechanism of which can be locked by means of a locking mechanism which comprises one series of pushbuttons (25) on each side of the lock. The pushbuttons (25) act on code and blocking tumbler members so that when the correct number combination is put in, one of the two check slides (39) is released. A selector (59) couples the two check slides (39) to the lock bolt actuating mechanism so that, when one of the two check slides is released, the lock bolt (17) can be moved to its unlocking position. The lock can thus be unlocked from either side of the lock and, due to the two locking mechanisms, a different number combination can be set for the two sides. The tumbler members each preferably comprise a first tumbler element, consisting of a base element and a code element screwed onto the base element, and a second tumbler arranged in the check slide and biased by means of a spring against the code element. With such tumbler members, it is easier to modify the number combination.