1677 Guinea help please

[youliveyoulean 24]

Good morning,

does anyone have any thoughts on what has taken place with the '6' in the date on this guinea? This was sold at the most recent London coins auction. They describe it as a continuation of the lower loop. 

Also, can anyone recommend some literature on the early guineas - I'm interested in the period up to 1760 (Charles II - George II).

Thanks.

 

[Rob 2,996]

Looks like a flaw to me. The last 7 could be over a 6 though

Edited September 12, 2018 by Rob