hideandseeker,
One of the fun parts of this hobby is to properly identify stamps. Sometimes, its like being a forensic investigator.
For example, if you were to go to 1847 USA (
http://www.stampsmarter.com/1847usa/), you would see how Clark made the identification. On the left hand side where it shows "1908 Washingtons", you will find the issuance of Washington-Franklin stamps by postage value and BY DATE. Click on it and you will see. Your stamp is postmarked 9/3/1910. It can ONLY BE a 352. Try it and see for yourself. Its fun to make an identification and then come to the group for confirmation. If you state the facts supporting your conclusion, others will see that "you did your homework" beforehand.
Hope the helps,
Jack Kelley