Welcome to the board, I'm sure one of the more knowledgeable Singer people will be able to answer your questions.
I love a nice solid vintage machine, but my excitement is more for the electrified post-war Japanese machines like a Morse or my Remington -- and even then I don't much more than "I like it".
Looks like Q stands for Queretaro, Mexico.
https://www.singersewinginfo.co.uk/193/