Just a note that the seat can be tricky pushing down to relieve pressure so the key doesn't break while turning the seat lock.
If it's the only ignition key you have I would take it so a house-hold locksmith to get a backup before it breaks. Super cheap (under $5 most places) if you still have a good working key.
I have something like the smaller key that came with an add-on document holder mounted between my license plate and plate holder. Little plastic box pushes the plate 1/2 inch back, still in the light. Not super-secure if you're worried about stolen registrations, except I've never seen another like it, and people just don't think about it being right there, so why would they start cutting there?
Sure the smaller key here could be a number of other things as well, as mentioned the teethe code does not look coordinated with the ignition/seat key.