I'd need a closer scan to be sure, but it looks like your embossed envelope is Scott No. U362. Catalog value is only 30 cents, probably less with the damaged left side of the envelope. However, there are some collectors who specialize in DPO's (discontinued post offices) and in the case of the 1903 Chicopee Falls, Massachusetts postmark, it is a DPO that was in operation from 1837-1963.
As to the comment about the two postmarks, it is a very common occurrence in the early 20th century for there to be a postmark on the front (place of mailing) and a postmark on the reverse, too (indicating the date it arrived at the receiving post office -- confirmed by the abbreviation "REC'D" in the CDS.)
Although I doubt these details will enhance the value of your cover much, curiosity had me research the names (as best as I could read them) on the addressee, which appears to be Mr. Wm. DeV. Foulke, c/o John W. Sidle, 628 Race Street, Philadelphia.
This research came up with some interesting information and the connection seems to make perfect sense. It seems William DeV. Foulke was an Officer in the Pennsylvania National Guard and was apparently a sharpshooter and even won a Wimbledon Cup for his marksmanship:
To further add to the historical relevance of the cover, the name John W. Sidle at 628 Race St., Philadelphia finds that he was a seller of a telescopic sight for rifles back in the day:
Posted 09/08/2014 6:41 pm
