The first reference to the manufacture [selling] of Lock Mortice Chisels (LMC) is found in the early 1861 Catalogue wherein the [Common] LMC [CLMC] is listed as being available in sizes 1/2″ ; 9/16″; and 5/8″. At this time they were only offered without handles. Also is listed an Improved LMC [ILMC], again with no handle and again in the same widths. The CLMC was a lighter-duty socketed chisel, whereas the ILMC was more heavy duty. It is probable that these chisels were manufactured for MARPLES, as the firm had no facilities, at that time, for such manufacturing.
By the year 1873 [the next catalogue available] the chisels had been assigned numbers. The CLMC being named #134 and the ILMC as #135. All widths available being unchanged from before.
By 1897 the numbers had been changed, but the option of buying with handles had been added. I will only list hereon the ‘handled’ numbers. The CLMC had become Item#134B and the ILMC became #135A
In 1909 there appear to be number changes..again. And also introduced is a lighter chisel named ‘London-Pattern‘. [This may have appeared prior to 1909, but I have no catalogues to show that.] This chisel was a tanged chisel, not socketed. CLMC Item #134B became #743 and ILMC Item #135A became #746. The new London Pattern LMC [LPLMC] in Boxwood was called #740 and available in Beech was #739.
1921 only sees Items 739; 740 and 746 as listed. The first two as available in 1/2″;9/16″ and 5/8″. And the ILMC #746 in Beech available in an expanded variety: 3/8″;7/16″;1/2″;9/16″ and 5/8″.
1928 lists the same chisels as in 1921. Although #746 is shown as being now available with an Ash handle.
1938 lists exactly the same as 1928
By 1959 there are only listed #739 and #740. And by 1965 there are no Lock Mortice Chisels listed at all. I must guess that plunge routers or other tools took over?