<VV> Early Rochester B/BC/BV Question - No Corvair

[Grant Young]

Hoping someone might be familiar with some early Rochester B series carbs that were on 50's and early 6 cylinder GM engines. I am rebuilding one for a customer off his '57 Chevy and noticed that there are some extra holes drilled in the cast iron throttle body that were not part of the original casting. In this particular carb, there are 5 of them about 1/16" drilled next to each other, apparently from the outside through a hole for a vacuum connection brass fitting. They are just above the throttle plate when closed, similar to the location of the ported vacuum slot in our H/HV carbs (so I assume that might be their purpose). I checked several other carbs I have of the same vintage, some used and three NOS ones. All but one (a used one) have the holes, but the number varied in size and from one large to 3 small ones. None are neat and aligned enough to be "factory." I am certain the ones in the customer's carb were drilled from the outside by hand because the person who drilled them was not careful enough and hit the throttle plate on 4 of them. Does anyone know of an early TB or old mechanic's tale that might have resulted in this? Thanks,
Grant