B
Billy Bob Bob
Come across that a lot on stuff fitted in the 70's and 80's. Some that are fully soldered you can snap off easily. Might be a combination of bad cleaning and the flux but it only seems to be on stuff from about a 10 year span. Saying that it is unusual to find soldered copper stuff from the 60's or earlier. It was all compression or paraffin blow lamps for lead then.
after 30 years warrentys probably void