Reply to u/BigZibby at https://www.reddit.com/r/typewriters/comments/1wuaui0/serial_number_location/
In fact, I do! You've probably asked the one person who's spent the time delving into the typewriter database to try to puzzle something out on this front.
I've not seen it in official sources, but the following pattern seems to fit:
Royal Standard serial numbers are generally of the form [MMM][P,E,S]-XX-YY-#######, where:
- MMM is the model designator (X, KHM, KMM, KMG, HH, FP, etc.);
- P is for 10 pitch/Pica, E is for 12 pitch/Elite, and S is for Special (typically special order typefaces);
- XX is the platen length, when not the standard/default size;
- YY is for other special features, typically the number of glyphs in the typeface; and
- ######## is the serial number.
Yours has a YY=86 which typically indicates that the machine has 86 glyphs on the slugs in the typeface and thus 86/2 = 43 character (typing) keys on the keyboard. There are also examples of other YY numbers like YY=88 with 44 keys and YY=92 or 46 keys versus the standard 42 keys. You may notice under your machine that the keyboard has a metal "comb" which may have some empty slots into which addition keylevers and typebar assemblies could be added. Often the YY designator is either for special order keyboards or keyboards for foreign languages which require additional keys.
Thus the 86 means that your machine has an extra key (the +/=) not found on their standard issue keyboard at the time.
