Professor A.S. Low
"Professor" Andrew Low looks a bit startled on his private die stamp. Perhaps it has to do with the abrupt change from being a partner in a cigar store to becoming a purveyor or manufacturer of a proprietary medicine. Or it may be due to some confusion about his middle initial. The Boston Revenue Book refers to the company as "Prof. A.P.Low" while Henry Holcombe writes about him as Andrew S. Low.
The Low proprietary stamps were issued from June of 1875 until March 30, 1883. 660,106 were printed on silk paper and 954,997 on pink and watermarked papers. This one is on watermarked paper.