National Team Srivers

I've read that Butterfly simply provide sponsered players with "centre cut" rubbers, but it's the same rubber sheets that are sold commercially.

This appears to be one of the differences to the Chinese, who create special formulations only available to Chinese elite players.

The Sriver you buy retail could have been cut from right next to the square sent to Timo Boll.

I don't know about that. but I know like the chinese national ones, the BTY ones also have a big stamp, unpacked in bulk.

The difference in cuts varies in their quality.  All sponges are made in giant blocks then they are sliced into sheets.  After that they are assembled to the topsheet and cut into individual sheets.  The sponge in the very middle of the block is the most consistant in sponge density, pore size, hardness.  Therefore, the pro's are given rubber sheets that have sponge from the middle and normal consumers are given the outside of the block.  Hope this helps.