Info about mamiya 645 "sample"

I recently bought this camera from eBay and am super happy with it (though it could be lighter). Had a pro model before and regret selling it now...

Anyways it has "sample" stamped into the side and I was wondering what this really means? I bought the camera knowing it was a sample, but I though the seller meant it was just used in a store rather than having the word physically stamped into the body as well.

This one is about a Mamiya 150mm f/4 marked as ''sample'' http://photo.net/medium-format-photography-forum/00ZVkZ?unified_p=1

macfred said:

This one is about a Mamiya 150mm f/4 marked as ''sample'' http://photo.net/medium-format-photography-forum/00ZVkZ?unified_p=1

Click to expand...

Thanks!