Grace's Guide is the leading source of historical information on industry and manufacturing in Britain. This web publication contains 130,460 pages of information and 207,760 images on early companies, their products and the people who designed and built them.
Note: Name is spelt both as Horstmann and Horstman
1955 Horstmann Gear Co started making veterinary equipment, first a bloodless castrator and a unique spring action earmarker, which was very successful
1955 Simms Motor Units acquired a controlling interest in Horstman Ltd of Bath. Horstmans made electric clippers, ground thread hobs for high precision gear cutting, as well as camshafts and similar products for most of the leading motor manufacturers .
Presumably this left a remaining entity which was called Horstman Defence Systems