Well it looks like I've got a new rule of thumb:
100 Koke beans = 11.8gms
100 BUF Cafe beans = 12.2gms
I looked up at the Dukundekawa, Senhora de Fatima and Amaro Gayo sitting in their jars and figured I'd gone far enough. With a statistical sampling of two, the new rule of thumb is:
100 beans = 12gms
;-)