From time to time, we have seen Yema chronographs that have been modified / re-finished to pose as (fake) Heuer chronographs, especially the Flygrafs. The link below will take you to an ebay listing that provides some interesting history on the Yema brand (including being James Bond's first movie watch, as well as space missions and sponsorships of baseball teams --??). I can't confirm the accuracy of this information, but thought some of our readers might be interested.

. . . and to close with the usual confirmation, I have no affiliation with the seller / no intention to bid.

jeff