I am new to Numista..need help

Hey, I am going through my coins and have found a 1902 UK one penny.  According to this site there is a low and a high horizon for this coin. What does that mean?  Also what is a KM# with a coin.  I can't find a meaning for this anywhere.  Can some one also direct me to a site that might be able to answer my newbie questions?
thanks
chris   

you can post your questions here if you like. other than that there are dozens of numismatic forums out there. pick yours.
1) low horizon means the horizon line behind "Britannia"-figure. In one variety it is higher than in the other,
if you have both you could easily determine which is which. In fact I don't know "how high or how low",
maybe someone else can give you a number to check yourself
2) KM# means the widely acknowledged Krause and Mishler World Coins Catalog number of a coin.
Different catalog systems use different numbers. You will come across different codes on numista.
KM# is Krause/Mishler as said, C# are often used in World Coins Catalog from before 20th century coins,
Y# are also codes used in World Coins Catalog used for countries not yet categorized by Krause / Mishler, I think they come from a catalog called "Yeoman", but I am not sure.
F# is Funck Notgeld Catalog , SS# is Schön & Schön and so on...

Here is a picture I just made, for Normal tide and Low tide (I put the pink lines on to show better)

Thanks alot!

Also a KM# is not usually unique for one coin in the world - it can be used for each country.
 So for example KM#1042 is used for four different coins - in France, Isle of Man, Spain, Turkey. The lower the number the more coins it covers e.g. KM#68 is used for 34 coins.
 And as years go by there are more coins issued (and more KM numbers therefore), so it is never-ending (until electronic payments take over) I guess!   

Quote: ZacUKHere is a picture I just made, for Normal tide and Low tide (I put the pink lines on to show better)

Good job. Thank you.