There are 3 versions of the Summilux-M 35mm f/1.4 Asph lens actually.
1st, Code 11873 - Aspherical is spelt out in full with 2 hand-polished aspherical glass elements. Very limited production and collector's status of sorts
2nd, Code 11874 - Asph, with a single asph element
3rd, Code 11663 - Current production with a single asph element and floating focus design
There's no end to learning all these codes!