And since I've mentioned GNU groff elsethread, here's where it today in its "ascii" mode uses a minus sign instead of the equals sign to do the very same thing as you did on your typewriter, for "Po", the macro for producing a pound symbol.
* https://cgit.git.savannah.gnu.org/cgit/groff.git/tree/tmac/t...
Weirdly, I learned to type on a second hand Selectric typewriter that my parents bought cheaply at some auction, and while it had a '1' key, the only ball we had used that key for punctuation instead, so we still needed to type 'l' instead.