I'll check that out. Thanks! Should have mentioned its on a postcard from Minneapolis, Minn. to Memphis Tenn. There is also a partial RPO cancel, "James and Min...." cancel. Maybe James & Minneapolis RPO?
Doesn't appear to be St. James, just James. What is showing before the James in the CDS is "RPO" that's following the second name beginning with Min... Googled St. Louis and San Francisco RR perfin and found a checklist of Railroad perfins. They did use "FL" as a perfin.
Postmark appears to be "James & Miles City / R.P.O." running between Jamestown ND and Miles City, MT. Mobile Post Office Society catalog # 874-V-1, known used in the 1911-1914 era. Yes, I seem to recall the "FL" perfin is from the Frisco Line, but do not have the perfin catalog in front of me at the moment.
Conductors on many RR lines sold stamps to passengers as a courtesy. Many of these contained the perfin of the RR line. Finding these on tourist-sent cards is common, perhaps even more-so than on mail from company business.