Joinery of base to sides


For a Phila. tall clock base joined to the sides of the base with DT's, which piece - sides or secondary wood base - is pins and which is tails? Seems most reasonable to me that sides of this case should be pins and the base piece tails, then the joint is locked together so the sides can't separate from the base horizontally. Are there some other reason(s) why this should be reversed?
I checked the two period American tall case clocks that I have access to and neither is dovetailed here. I've gone through some of my references but none show this connection or give that much detail on the case construction.

I'm not sure it really matters as this joint is not highly loaded. The primary load is straight downward as the case must support roughly 30 lb of movement, weights, dial and pendulum.

You might try contacting the NAWCC Museum or some of the other places mentioned in the Snyder Clock Collection at Rock Ford Plantation thread a little below this one.