A subgenre of commercial postcards turned up in substantial numbers in antique stores. Some have messages and even dates.

Tis one was sent from Tijuana MX in 1911, to Mrs. C.H. Eaton in New Minas, NS:
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The message on the back:

Notice the River we had to ford going into Mexico. This is a queer place. The houses that are left standing are full of bullet holes, from the recent fight. All is quiet here now. We go back to San Diego this PM. The weather is lovely here and I am enjoying the trip fine. Hope you are better. Yours, H.A.L June 25/11 Mexico

This one was produced in large quantities and overprinted with a location:
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Most unlikely that the original pictures were taken in Nova Scotia (the water is coooold), but the postcards were sold in Nova Scotia:

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