Sacha

Corrected entry: When Old Biff hands Young Biff the Almanac, the book passes through the film split (the vertical bar that divides the windshield) perfectly because it was on a motorized rig. But the stand-in for Old Biff didn't hold his arm at the right height, so Old Biff's arm disappears into the bar that runs down the middle of the window while the book floats across to Young Biff.

Correction: No it doesn't. The arm is below the windshield, that is why it can't be seen. The tip of the hand is perfectly visible, with no missing parts.

Sacha