The most valuable 1907 $5 Federal Reserve notes are those with low serial numbers and desirable signature combinations. For example, a note with a serial number below 100 or a note signed by both Lyman J. Gage and Frank A. Vanderlip can be worth a premium.
If you have a 1907 $5 Federal Reserve note, it is important to have it professionally authenticated and graded in order to determine its true value.