RCCS is Royal CanadianCorps of Signals. Not sure on the "B" and the "III" but possibly B Company.
RCA is Royal Canadian Artillery. The line between the RCA and the 55 is a cancellation mark and can be a straight line or look like an aeroplane propeller. The 55 is the battery number, and the 24 is the rifle rack number, or, the 24th rifle issued to 55 Battery.
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