Dutch mastering and lacquer cutting engineer at Bovema / EMI Studios (aka. [l279948]), Soundpush Studios and at Wisseloord Studios.

Because HH was already taken by Gerard Hali, Horden chose M (after his girlfriend Marianne) as his identifier for cuts at EMI / Bovema Studios since 1971.
So, in case of HM, e.g. -A//HM 18729-1, please credit with
Lacquer Cut At - Bovema / EMI Studios and
Lacquer Cut By - M

Lacquers cut by him at EMI/Bovema since 1971 can ocassionaly also be recognized by an additional etched Henk or H.
Please add Lacquer Cut By - Henk Horden + ANV Henk or H