Here is a view of two three-masted schooners being loaded with granite. The scene is what we now know as Granite Pier and which was then the pier of the Rockport Granite Co. Compare this postcard with this other one (also shown below) from the same publisher. It appears that both of these pictures were taken the same day, from different vantage points. The same two schooners are visible in both pictures and you can see the same buildings on the pier in both.
The above postcard and the one I posted earlier were both published by Souther-Mears Co., a Boston company that was in business only from 1908 to 1910. The card was distributed by A.M. Simon, a New York City post card publisher. The card was printed in Germany using a process known as collotype, which was used because of the accuracy of the reproductions it produced.
This postcard is postmarked Aug. 20, 1913. Given that Souther-Mears was out of business by then, and that it appears to be from the same day as the earlier card, I estimate it is from 1908. Of course, even though the card was probably produced in 1908, the image could be from even earlier.