Nope, it's not. It is just a vintage Seiko strap. I know it could be considered as an heresy but I like the way my 145.012 stands on it.
Bertmar was a name applied to their house brand watches by People's Jewellers (People's Credit Jewellers). The founder of the firm, Frank Gerstein, compounded the name using the names of two of his sons, Bertrand and Marvin. Just thought you should know. Thanks for showing it!