There is no difference in a regular common share and a Class A common share, except on the books of the corporation.

The corporate by-laws have designated that, of the 75,000,000 shares authorized, 500,000 are considered different from the other 74,500,000 in that those 500,000 each have 200 votes.  Those 500,000 are given the designation 'Class A' to differentiate them from the other 74,500,000.

When the Board says "BG, you need to own some Class A shares, so nobody can take over the company", he buys some shares (just like he would buy regular shares) and they are designated by the Board as Class A shares.  He can have those because he was a Board member and they authorized him to own them.  On paper, those Class A shares look just like a regular share, except they have special voting rights.

When BG is no longer a Board member, the By-Laws stipulate that his Class A shares automatically become regular shares.  The Board can then specify another Board member to buy up to 250,000 shares of stock that they can specify are Class A shares.