first dial 17 as shown in fig4 as better shown in fig3 the lock tumbler 28 has an integral pin 31 axially extending on opposite sides thereof and having both of its ends guidedly received in an elongated guide groove 32 formed vertically in each of the side walls 13b and 13c of the casing 13 the tumbler 28 is normally urged downwardly and clockwise by a torsion coil spring 33 wound on the axial pin 31 on one side of the tumbler 28 and having one arm 33a supported on the top wall 13a of the casing and the other arm 33b supported on a retaining lug 34 projecting from the tumbler 28 above the first lock pawl 29 as better shown the slave lock unit 12 is cross sectionally u shaped and has a pair of guide grooves 35 of a predetermined length formed horizontally in opposite inner side walls 12b 12c and adapted to receive corresponding ridges 36 projecting outwardly from the respective side walls 13b and 13c of the casing 13 this ridge and groove arrangement 35 36 allows mounting and dismounting of the slave lock unit 12 with respect to the master lock unit 11 the dial lock assembly 10 is shown in fig4 as in truely locked position in which the slave lock unit 12 is united with the master lock unit 11 and more specifically in which the first lock pawl 29 has been received and rested in the lock groove 27 which has been aligned in registry with the opening 26 in the base wall 13f and the second lock pawl 30 has been brought into abutting engagement.