First computer with real-time clock?

I once used an old computer made by 3M that was transistorized and used a magnetic drum as main storage. The machine was actually two processors, each of which fit in 12U rackmount drawers. Along with the two processors was another 19" 6' tall rack full of acquisition electronics...DACs, comparators, and counters, which were peripherals to the CPUs, which had I/O instructions to talk to the stuff. Included in the rack full of electronics was a real-time clock that kept track of the time in HH:MM:SS format. It did not keep track of the date, only the time. The clock was transistorized, using ring counters. The clock also put out 1Hz pulse that set a flip flop that could be polled, and reset by the CPU. I used this 1Hz signal along with the time from the clock to maintain date/time in a small operating system that I wrote for the machine as a class project. As I recall, there was no interrupt capability on the machine. The clock had a front panel display that showed the current time, as well as controls to halt the clock and set the time (advance hours, minutes or seconds). As I recall, the clock derived its timing from the 60Hz AC power line. The clock could he read by either CPU by accessing a read-only peripheral register. The time was returned in BCD format. My understanding is that the machine was designed in the early 1960's. It was designed specifically for data acquisition processes. I've written to 3M to try to find out any information they may have, but alas, none survives. Unfortunately, I can't remember the model number of the machine. The machine I used was donated to the high school I attended sometime in the early '70's, after being used for quite a long time as a natural gas pipeline monitoring system at Northwest Natural Gas in Portland, OR. The machine used a 24-bit word, with two-address (operand & next instruction) format. Opcodes were 5 bits in length. It had a hard-wired "read in mode" where it would accept input from a teletype (ASR-33) in the form of octal address followed by a space, followed by the data to be written to that address. Addressing was stated in block/track/sector format. The instruction set included information for optimal programming to allow for the rotational latencies of the drum. The machine was rather slow, even when programmed optimally. I recall that I had a hard time writing code that could send output to the teletype at full speed. Rick Bensene The Old Calculator Web Museum http://oldcalculatormuseum.com