At one stage I had 23 nash / neville stainless alarms and I also have 5 of the green versions ....
There was a difference , to my knowledge (please correct me if i am wrong) the 1st batch that came out were more of a brushed steel finish with a one way switch without the nash logo , the 2nd phase alarms were a polished steel version with a one way switch and a nash logo on the speaker , the 3rd phase of alarms were a polished steel alarm with a 2 way switch and nash logo on the speaker all alarms had the little black rod protectors on the ears .... I sold 6 alarms of the brushed steel version as I preferred the look of the polished finish ...