From the USPTO site:
Word Mark RUMPP
Goods and Services (EXPIRED) IC 018. US 003. G & S: BILLFOLDS, LETTER CASES, TOILET CASES, PHOTO CASES, PASS CASES, CARD CASES, AND KEY CASES. FIRST USE: 19450301. FIRST USE IN COMMERCE: 19450301
Mark Drawing Code (3) DESIGN PLUS WORDS, LETTERS, AND/OR NUMBERS
Design Search Code 26.15.27 - Keystones
Serial Number 72240085
Filing Date March 3, 1966
Current Basis 1A
Original Filing Basis 1A
Registration Number 0831667
Registration Date July 11, 1967
Owner (REGISTRANT) EVANS-ARISTOCRAT INDUSTRIES, INC. CORPORATION NEW JERSEY 400-416 TRUMBULL ST. ELIZABETH NEW JERSEY
Type of Mark TRADEMARK
Affidavit Text SECT 15.
Live/Dead Indicator DEAD
Not the exact mark we see on the flask, but it does show that Rumpp officially used an "R" in a keystone as part of their trademark.