Hard to say with so few letters and in such a condition but taking in consideration /C and /S terminals angle looks rather parallel to baseline would confirm your hunch for Helvetica/Helvetica Neue (the 2 versions are different). Neue Haas Grotesk would work as long as many other Helvetica clones/digitizations/reinterpretations like URW++ Nimbus Sans, Paratype Pragmatica, Scangraphic Europa Grotesk, Bitstream Swiss 721...

That was the problem I was running into. I can find the same C, with the narrow opening, but every font that has it uses a B that is offset top and bottom. The fonts with a symmetrical B have a C with a wider and non-horizontal closing. It's driving me up the wall!

Right now I have a composite of Helvetica Neue LT Standard for the AC and S... but I have to use Helvetica Standard for the B. It's the closest I have gotten to the original font.