I don't know the specific model Mark, but 8mm will give a circular image on a full frame camera, or of course film, and it will give an enlarged circle with corners missing on an APS-C sensor. Due to the lack of rectilinear correction it will give a much wider view than your 10mm - way more than the 2mm difference would suggest.
Samyang always used to be Korean manufactured, sold in the UK under the "Sirius" name and were generally at the lower end qualitywise, though they made some interesting lenses - I used to have an 18-28mm lens of theirs which was pretty OK when stopped down a bit.
You'll have to be careful to keep your feet out of shot
