New Find: R155 with St. Louis, Keokuk, and Northwestern Railroad Printed Cancel

Mike Morrissey has sent a scan of a Fullerton unlisted railroad item: an R155 with a St. Louis, Keokuk & Northwestern Railroad cancel. 

ST. L., K. & N. W.

R. R.

St. L., K. & N. W. R. R. cancels have only previously been known on R163s, both roulette and H. H.  Frank Sente figures the stamps were used on checks.  I would guess this likely, but if so, where are other examples, either on or off document?

If you know or possess an example of this cancel on an R155, please report it or send a scan of the stamp to:  1898revenues@gmail.com.  Thanks!