10 Pesos Gold Bullion Cover

1940 JUNE 5: MANILA to SAN FRANCISCO
15 Pesos total franking matching the indicated blue crayon "15--" rate.
ONLY THE SECOND 10p ENTIRE COMMERCIAL COVER THAT I HAVE SEEN. The stamp also exist on three parcel pieces.

I don't think the number of bids received is a clear indication on how many collectors aspired for this cover. The bump from just over  $150.00 to above $500.00 gave no opportunity for other bidders to jump into the pond. 

Expensive at $518? Not to me. The closing price hurts but I am certain it will immediately go away once this cover is in the hands of the buyer.