Just following this thread.
I don't think it's a good buy. Afrikaans are abusively hard on guns and they have never heard of gun oil. This looks like a parks rifle rode hard, put away wet.
Cons: condition, price, not a Mauser, no collector value, restocked, post war manufacture.
Point of reference: I bought a Cogswell & Harrison post war .375HH recently. (1951) Very good serviceable condition. Built on a Mauser action. Paid $2550. Believe it's worth $3500. Based on my appraisal and what I paid for what I got, I believe your 404J is worth $600-$800. It needs a lot of work and $1000 would get you a brand new CZ550 in 404J that would be more reliable.
Cogswell made a LOT of field grade 375 and 404 rifles over the years. Fairly common. They are in my opinion superior to a pre64 model 70 and usually cost marginally more. The issue with the gun being discussed is the fact it's not a Mauser and it's in dastardly shape.