Paul ,
Assembly line header gaskets were white asbestos. You "must" keep in mind that Cyclone did not make their own gaskets and bought them from more than one supplier. Same for Doug's and Bellanger. many used a local company called "Best gasket" and your picture looks like one of those. Best probably made their pattern off of a flange supplied by Cyclone . Best used to imprint the company name into the asbestos and they are very rare these days just like white asbestos material is. Other companies used the Raybestos Manhatten ( R-M logo and blue ink) material but "I" never saw it used on SAI production cars. By my memory "flat top" gaskets came with the Cyclone stuff and the "bumpy top" gaskets came from Doug's and Bellangers because they were made off of a bumpy top flange they used.
It would be hard to validate NOS on a loose ( non packaged) gasket , well IMHO anyway.
Randy