Can I put the Knowlton award on my ERB?

Sadly, It does not get entered in the ERB. At most, you can get it mentioned in an NCOER. I have done a lot of research on this issue. I have the Order of St. Barbara (FA), the Sergeant Audie Murphy Club Medallion (FORSCOM), and the MG Aubry "Red" Newman Award (FORSCOM). Regimental and MACOM awards fall in the category of badges of quasi-military societies.

At the time of my research, 2002, certificates were not placed in the OMPF/IPERMS. This may have changed. (Army Regulation 600–8–104, Army Military Human Resource Records Management)

AR 670-1, para 22–12. Badges authorized for wear on Army uniforms
d. Badges of civic and quasi-military societies of the United States and international organizations of a military nature. These include badges of organizations originally composed of members who served in a U.S. force during the Revolutionary War; the War of 1812; the Mexican War; the Civil War; the Spanish-American War; the Philippine Insurrection; and the Chinese Relief Expedition of 1900. These also include badges (such as medallions) issued by military (regimental) associations. The badges are worn only while the wearer is actually attending meetings or functions of such organizations, or on occasions of ceremony (as authorized by the commander). Personnel will not wear these badges to and from such meetings or events. Items must be similar to those authorized by AR 670–1 and worn in the same manner.

It used be the luck of the S1 clerk you found.

Add "awards", "S-1", "HRC", "ERB", and other applicable tags for more attention to this thread. If its anything like the Bronze order of Mercury for Signal Corps, I'd suggest you get a copy of the paperwork put in your OMPF.