I'll Be There Soon to Tell You How to Jinger Up Your Trade
"I'll be there soon. And say, I've the best you've seen yet. Wait till I tell you--Ha-Ha-Ha-Ha! How to jinger up your trade. Competition. Samples. A. C. No. 6. Copyright 1907. Published by K-Win, Chicago."
Unused "advance card." Salesmen, or "commerical travelers" as they were called in the early twentieth century, sent postcards like this in advance of their trips in order to notify merchants when they expected to arrive in town. They traveled by train with heavy trunks or "sample cases" (like the one that the fellow here is riding on) containing their wares, and many hotels offered "sample rooms" where they could display their merchandise.
By the way, I suspect that "jinger up" was intended to sound the same as "ginger up," so a salesman who sent a card like this was offering to liven up or spice up the recipient's business.