I don't know, My Man Godrey is from 1936 and the Criterion DVD has outtakes, and they're actually really funny! I'd like to see more bloopers from older classics.That's just one film. Outtakes are still very rare, even if a few scraps re-surface. The only other outtakes of classic films I can think of are...
"Scarecrow Dance" from The Wizard of Oz
A few animation outtakes from Snow White
The deleted "Clair De Lune" from Fantasia (Which was partially in another film)
Countless takes from City Lights
Outtakes from Sunrise
This is just a few films...out of thousands made before 1970.