Yet another Sam/Rok/Bow distinction question

[slclick]

Does anyone know if the features are truly any different on these two lenses? The Rok has a couple extra letters thrown in on the description. I'll take all the magic pixie dust I can get.

 

[Hector1970]

Looks like the difference is ultra-multi-coating which is for reducing lens flare.
This might be a help in a lens like this.
Whether it's effective I don't know.
I have the 8mm Fisheye for APS-C.
I haven't used it in a while but it is a good lens.
Their 14mm is very good too.