Domestic High Arm Fiddlebase: What are the extra holes for?

I'm having tons of fun with a Domestic high arm fiddlebase treadle that I picked up for $35.  I had been wanting something like this to play with, where I could do whatever the heck I pleased without guilt.  You will see what I am talking about later.  Perhaps much later---I never know how long these things will take.

So here's the quick question:  What are the extra holes in the wooden top for?
There are holes for the treadle belt.
There is a hole corresponding to a hole in the front center of the machine that I think is for a bolt to secure the machine down. It is drilled all the way through
There are holes for the bonnet top (sometimes called "coffin top", ewww).  Projections on the bonnet top slide into the holes to keep it in place.  These holes are in metal.
There are holes for the pins or projections on the bottom of the machine to rest in.  This keeps the machine firmly in place.

However there are a set of extra holes.  These are drilled about halfway through the top, and were filled with what looked like bathtub caulk.  On top of each one was a felt pad, each one secured to the wooden top by the tiniest pins I have ever seen.

The holes for the machine pins (small bumps on the bottom of the machine) are identical to the mystery holes.  They are the same size and also drilled about halfway down into the wood.  Because I stupidly did not take "before" pictures, I can't swear as to whether they also had the caulk and the felt.  

I "get" the felt pads, which would cushion the machine, protect the wooden top, and probably cut down on noise and vibration.  What I don't "get" are the caulk-filled holes.

Any ideas, o brilliant ones among you?