It is the W.H. Allen, Son & Co. Ltd. in Bedford, England.

Between 1910 and 1919, especially during WWII, Allen along with Bristol built the Gnôme Omega, as well as the Le-Rhône 9C, 9J and some 9R to power the Handley-Page, Bristol, DeHavilland, Sopwith and Avro aircraft with an amount of more than 10,000 engines.

From Appendix 6: Now we show a picture of an engine of this type built by Allen.

“Allen-LeRhone, from 1918”