The first Series 16 machine I used was a DDP-516 machine. This was installed in my secondary school; The Gateway School (now Gateway VIth form college), in Leicester, UK.
The school had been given the machine by Leicester Polytechnic (now DeMontfort University) which is located across the street from the school. The DDP-516 had been installed in the Polytechnic's computer centre to provide a general purpose computing resource for teaching computer science.
The DDP-516 machine had many of the CPU options and optional peripherals; Extended addressing, Memory lockout, High speed arithmetic, Real-time clock, Direct multiplex control, High speed paper tape reader and punch, Line printer, Magentic tape, and Moving head disc file.
When I became interrested in the DDP-516 it was not functioning properly. In fact it had never worked since being transferred from the Polytechnic. I had been interested in electronics for some time as a hobby. I found the Honeywell fascinating; far more interesting than the 6502 and Z80 based microcomputers that were otherwise available. This machine had a CPU with schematics!
Eventually the DDP-516 was fixed, at least to a useable level, though the magnetic tape and disc never worked. The machine was used for a while in teaching computing at the school.
The school was then given another machine by the Polytechnic. This was an H316 model which had been used by the Electrical Engineering department. This machine was in fully working order and was used in parallel with the DDP-516.
After myself and the small group of others students who kept the Honeywell machines working left the school, the Honeywells continued to be used for a while but slipped into disuse as more microcomputers became available. When the school finally decided to dispose of the computers (this would be in 1984, I think) they contacted me. I was able to rescue the H316, though the DDP-516 was far too big and heavy to provide a home for and went for scrap.