Duncanv:
Think about it - what would make that cover worth more? Logically, the following would:
- Better margins all around (the bottom is cut into)
- A rare origination or destination (Wilmington, Del to Philadelphia is nothing special. Indian Territory [Oklahoma], is special)
- Something else going on on the cover (see below)
- A better stamp. The 3c is the most common stamp of the era. An imperforate 1c stamp is scarcer, some varieties of the 1c imperforate are worth >$50,000 on cover. If it had a full margin 5c imperforate, it would be worth >$500, regardless of anything else. An imperforate 10c stamp would be worth >$100 regardless of anything else. Same will hold true for the perforated versions of this issue, as well as the 1861, 1869, and virtually any other series of stamps.
- covers with multiple stamps, multiple denominations, etc. would add to the value.
Now, here are some "better" imperforate 3c covers:



That help?
C.