Query Regarding 2 N.y. Cancels On Canadian Postal Card

Hi y'all!
Can anyone explain to me these two New York cancels on this postal card sent from the Bank of Montreal in Brookville Ont. Canada in 1887?
Shown are front and back of the card. The American cancels on are on the left on both sides. Similar, one on the front reads P.O. (post office, obviously) along with the date (4-2-87), a code 7-1A (the postal worker?) and N.Y.. The one on the back is similar, but with a large C in place of the P.O. and a different code.
The card was sent to the New York County National Bank in NYC.



Receiver cancels? Postal carrier cancels?
Thanks in advance.

P.O. is a receiver for New York City. C is probably a secondary one used by a NYC clerk or postal station for final delivery. I think the "10 A" there is the time, pretty typical of receiving cancels of the era.