I suppose there must be any karatage of gold out there. Obviously the amount of pure gold found in an alloyed metal would affect it's value. Gold is typically alloyed with other metals to improve it's robustness and make it easy to work with (pure gold is a very soft metal and in passing through many hands as say coinage, would tend to rub itself away)

8k gold would be one-third gold alloyed with two-thirds other metals. It sounds marginally worse than the 9k crap sold by jewellers in the UK. (24k is considered pure gold)

It's entirely possible and plausible that some person, organisation or even country has minted coins at such a low percentage of gold - for example, the amount of gold found in Roman coinage paid to centurions struggling to maintain Rome's failing empire was very low. The number of soldiers going AWOL was incredibly high, and corruption must have been rife.

If you were looking to invest in gold - buy something closer to 24k - with minimal contamination.