Authentic boards are made of pvc plastic and normal come in a plastic sleeve for protection. Though fake pencil boards are not normally found around most online store you must keep watch for them when more rare boards are offered on such pages as Ebay and in newgroups. If there is nothing mentioned about its origin, email and ask the seller before purchasing or bidding. It may be a Hong Kong or Taiwan made copy and the seller may not know or may have failed to mention it. Most reliable seller well mention its board number, or that it is authentic.
All online stores list only sell authentic japanese pencil boards.
This means that there is a 1296B and possible a 1296B and 1296C and so on. This is noramlly found on the back of the board normally in the bottom left or bottom right hand corner. Normal original price for a board is 250-300 yen depending on if it is double sided, single sided, or clear. Most compnaies, like Animetopia, follow this same system, but some numbers are different. These are usually just classified by the company name and description.