This article is an update – along with some additional information and insight added. I published the results on the reflector and, in the years since, I have continued to gather additional data from other sources. The project was designed to shed light on the many questions collectors had about production quantities, anomalies, scarcity, etc. 51S-1 HF Receiver – Blocksome By Rod Blocksome, K0DAS A number of years ago I conducted surveys of Collins ham equipment on the CCA reflector.Collins 51s-1 Serial Numbers Average ratng: 3,8/5 4812reviews