Ford, with his bionic caliper eyes, thinks it is a 9.8mm but either way there is enough knowledge base here to cobble up about anything. I don't know if it makes any difference but it seems the tubes are reversed for a typical combo. It may be that the English preferred one arrangement while the Germans another? Anyway it may be a 360 BPE or some 10mm variant.
I can't say what the founding date which surely was prior to 1880, but by 1900 the owners were Heinrich Diehl & Heinrich Ludwig Jost. Jost & Diehl sold hunting and fishing haberdashery as well as sewing machines & bicycles. Both may have been businessmen but somehow they had to have a master gunsmith on staff to peddled sporting weapons. Heinrich Ludwig Jost was the a partner, the business component and probably the money man as his name was 1st. In 1927 there were at Hafergase 15 in Worms, Germany & had a telephone number of 731. I would guess the example to have been made between 1873 & 1882 and components may have been sourced from Birmingham.
Kind Regards,
Raimey
rse
