You know what's funny? It would probably be easier/cheaper just to go to a thrift shop and pick up a Model M, instead of doing some dubbing effects.
No it wouldn't and incidentally that is also why they don't .
It's often easier to 'design' a sound than it is to capture the real thing
'on tape' .. Furthermore, the designed sound will often sound more realistic than the real thing !
Where I live we even have a government-approved education
for these people, 'Tone-Mester', translates to something like 'Tone-Master' .
You can either take a 2 year (full-time) candidate-grade or a 3 year (full-time) bachelor ..
And on top of that, you can spend another year and specialize !