Greg, Thank you for your fantastic response! I actually was led here by researching many times in various search engines. I have (1) 551B KSU with 118A RG, (2) 551C KSU's with only (1) 118A RG and 20 or so 2565HKM sets in a few colors. 5 COM-KEY 416 (2) main and (3) add on sets. I also have a collection of Merlin 820, Merlin 820D2, 1030, Merlin II and nearly every style Merlin Voice Terminal. I have been a telephone enthusiast since I was 11 or 12. My grandfather worked for Sears as a TV and Radio repair technician. As a youngster he taught me how to component level solder on boards. I can do some component level testing, however that is the limit to my knowledge. Sometimes my 61 YO brain gets ideas and I just want to experiment. My parents had a sheet metal fabricating shop. I was in sales, an estimator and a buyer for his company. In the early 80s I was able to get a private guided tour of the WE chip manufacturing facility in Reading PA. It was a guarded facility on top of a hill that not too many knew was even there. We were a sheet metal components manufacturer. As large as WE was they became a customer. We made a few prototypes for them, and only 1 small run of about 500 pieces. They also payed almost immediately.