[NostalgiaRadioTime]

Doing a little further investigation, block 4989-AH was later replaced with 4989-ODG, which had two .1 caps inside. That block is listed on the page I linked to above (scroll a bit further down the page). Basically, one end of each of the two caps go to the ground terminal, and the other ends go to terminal 2 and terminal 3 (making the three connections you see coming up). As to the why it only shows one cap on the schematic, possibly it was a revision they missed making in print? Who knows for sure what they were thinking 83 years ago.