In early 19th century Galician death records the column for recording the name of decedent's father often contains the word that appears to be "selbss" or "selbst". Does this mean that the decedent appeared himself (or herself) with no one able to inform who the father was?
It could mean "the same".
So Moses ben Nathan's father would only be known as Nathan. Just guessing.
-- Evertjan Hannivoort. The Netherlands. (Please change the x'es to dots in my emailaddress)