Identify these stones' grit

[rrc]

I live in the Czech Republic and picked these stones up at the local hardware store. They are confusing the crap out of me because the only grit-ish markings on them are 150/320, but it doesn't seem right at all because the red stone is a lot smoother than the green stone, but they both say 150/320. They also don't seem rough enough to be such a low grit, but I really wouldn't know because this is my first attempt at sharpening ever and these are the first stones I've ever handled. The 49C and 99A don't mean anything to me, nor does the N and O markings. The green is marked as Carborundum, so that makes sense, but I don't know what Electrite is...

http://oi44.tinypic.com/5btd85.jpg

The manufacturer's website does have an English translation...

 

[HeavyHanded]

I'll take a guess and say the grey one is silicon carbide and the reddish one is aluminum oxide. You'd have to send an email to the company to find out for sure. You'd be surprised just how "smooth" some of these stones can feel and grind, especially if the final surface lapping at the factory is above average.

 

[Obsessed with Edges]

I'm looking at the web site of the "Carborundum Electrite" company, as indicated on the boxes in your pic. It's a Czech site, so I've used Google Translate to find this (excerpted) info in the 'Who We Are' description on their home page:

"The oldest European manufacturer of abrasive tools made of synthetic corundum and SiC"

Synthetic carborundum is also known as aluminum oxide, and the 'SiC' refers to silicon carbide. So, I think HH's assessment is likely accurate. The colors are somewhat similar to Norton's India (orange AlOx) and Crystolon (grey/blue/black SiC) stones.

Here's the site I'm looking at (via Google Translate):
http://translate.google.com/translate?u=http://www.carborundum.cz/&tl=en

 

[Obsessed with Edges]

Found this reference to 'Electrite' in a Google Books search result ( http://books.google.com/books?id=B3_nAAAAMAAJ&pg=PA415&lpg=PA415&dq=electrite+abrasive+-electric&source=bl&ots=fIizfqbkah&sig=lL6QR1iV-TyARC_7zhaH4MQT0as&hl=en&sa=X&ei=PX_7Toi9HdHRiALas5mxDg&ved=0CFMQ6AEwAg#v=onepage&q=electrite abrasive -electric&f=false ):

Seems to describe it as a slightly different variation of carborundum (Aluminum Oxide), book/article dated from June 27, 1907 (wow):

 

[rrc]

That is some amazing detective work :-D

 

[Obsessed with Edges]

That is some amazing detective work :-D

I'm not sure about that, but it's fun (I'm learnin' something new as I go here).

That 'Electrite' description almost makes me wonder if the dark/grey stone is the true 'carborundum' (box is labelled so), instead of silicon carbide. Might have two 'flavors' of AlOx hones there. Still trying to process what the '150/320' numbers imply (I'm assuming it is grit size, but to what grit standard?).