US Parcel Post - Postcard Question

Hello all. Today I visited a quaint little antique store around the corner and picked up a few interesting postcards. This US Parcel Post Stamp on Buffalo N.Y. postcard, was it only used in 1913? or were these stamps used on covers and postcards frequently? I believe this postmark is 1913 - but as you can see, there are two on top of eachother.

I do not delve much into covers and postcards, but I liked this one and it was probably sitting in that store for a long time with not much interest - the other two are nice from 1907 and 1913. Thanks. Nora.

Parcel post stamps were restricted in use use until July 1, 1913, when they could be used on any type of mail. Finding them on postcards in the last half of 1913 and through 1914 is very common. The card you show was fed through the cancelling machine twice for some reason.

Hi John. Thank you very much. Makes sense. :)