Honeywell IPC / ISSC PLCs

I found another rare PLCs. First I found on ebay some PCBs with some strange lead patterns. The original manufacturer was ISSC (Industrial Solid State Controls, Inc) located in York, PA founded in 1963. In Europe they used IPC (Industrial Programmable Controller). At least some PLCs were later sold by Honeywell and Klöckner-Moeller. Also distributed by Cutler-Hammer. ISSC is now a division of Kanson Electronics but only making timers etc. Here a RAM card with the most interesting pattern

The earliest model I found is IPC-4000 in magazine Electronics (1972-10-23) including a b&w photo. I first wasn’t sure about the model of the PCB pictured, but it must be from a 300. I think related to model 90, both ~1982. I haven’t found any details of these.

At least I found a manual of Honeywell IPC 620 (~1985). The CPU is a 6809 using BASIC09 but could be just for exchange with a PC. One needs an MS-DOS Loader and a Loader/Terminal software. Unlike the 90 and 300, the 620 rack is small and rectangular with a silver front. Cards have a partially opened beige plastic case. Digital modules have “double swing terminal blocks” see manual).

The manual is quite detailed. Registers have 17 bits 16+sign bit. A word has 24 bits, MSB first. Bits 0-15 for the address, bits 20-21 are “history” status bits. The rest for the instructions. There are relay logic instructions for the 1-bit i/o (ladder logic, checking AND/OR). And some other instructions like skip and timers. Arithmetic instructions using 16 bit signed, a division 32 bit signed numbers.
There are also details about the system operation but I think is the same for all PLCs (cyclic checking of i/o and actualize the outputs).

Next to a PC, there are also smaller, cubicle programming devices with few keys. Obviously mainly or only programmed via ladder logic. So an instruction look like this -] [-342 (OR address 342). The states are stored to a status table. Some cards support “ARMP” Augmented Run Mode Programming.

Most of interest the opcodes starting on page 46

Any more or better info or where I can find more vintage Honeywell PLC docs?