I was just asking Rich that same question and the answer was:
The silver we have been using is from PPG's Global paint line. It
is not a formula but the mixing toner BC769 extra fine silver. The Sherwin
Williams equivalent should be toner # U7006. There shouldn't be a
compatibility problem using Sherwin Williams clear on top of the PPG
silver. We have used it many times with success.
The paint line is at the base of the raised instrument pod area.
Hope this helps,
Rich