The Worksop badge puts this from 1962 onwards... that bit is easy. Looks like it does not have wrap over seat stays, so possibly not a Snipe model - they tended to have wrap overs, also the lugs are wrong (they are similar to the later Crespera lugs and the headset lugs look very similar to the Carlton '10' model). Thing that is odd is the frame number prefix letter. C would mean its maybe mid 60s (using the new Sun numbering system)... problem is that Sun adopted the Carlton number approach when Carlton started to make them in the same factory at Kilton Road. However... some people have suggested that the numbering system was restarted then ie at A for c1962, this would place the machine around about 1965 which would be about right. If this had the Carlton numbering, and assuming its mid 60s, it should have a M prefix maybe N. Basically its all very confusing... The all chrome front fork might be a clue to the model, assuming none of the other parts on the bike are original. Checking the VCC library is a good start, they have a few Sun catalogues on there to view. Also I co-run a Sun Group on Facebook - Sun the Birmingham Years, they are a good source of Sun enthusiasts, also there is the excellent Carlton Cycles of Worksop Group too. As to nailing this model, its a bit tough... the lugs don't say Snipe, but the front forks (with their typical Carlton Vagner crown) suggest maybe a Mass Start 100 model, however the lugs dont match... A bit of detective work is needed and maybe some educated guess work. Nothing surprises me about these earlier Suns and Carltons as always something comes along which seems to not fit into any known model or spec...