My Viking is also a 6.3 that takes 120. It's a decent basic folder with a triplet lens, and it seems to keep the dark in effectively (unlike many Agfa folders---I think the Vikings might have had more robust bellows material than some other models).

The lens on the 6.3 models seems always to be labelled "Agnar Anastigmat", on the 7.7 models just "Anastigmat". I don't know if that's an actual difference in the lens design or just a change of labelling, but as far as I can tell, the 6.3 models are German-made (Agfa) and the 7.7 models US-made (Ansco).