Mortised is loaded with alternate letterforms, ornamental extras and some quirky numerals. Herman Ihlenburg designed and cut it, patented it in September–November 1884 and assigned it to MacKellar, Smiths & Jordan.
The tradename touts its also-patented mechanical features (MSJ catalog, 1885):
“This is a unique and handy type that may be used not only for regular display lines, but more than half of the letters are so slotted or mortised on the sides as to admit of the insertion of types of smaller bodies, thus producing novel and striking effects which are heightened by the aid of the extension ornaments. The letters C, E, F, L, Q and T are made each in two distinct widths.”