Surfing the Marvin website, I found an email address dedicated to "vintage Marvin" so I sent a mail in order to obtain some information about my watches..
The answer was disappointing: "...After checking, we are sorry to inform you that we cannot give more details about your watches as we lost an important part of our company archives...". Since my watches range from the 30's to the 70's, what part of the archive has been saved? Why offer a service they aren't able to give?
Had a similar experience as @bubba48 when I emailed Marvin 2 years ago looking for information about this watch. They were very friendly but said they had little archive material from that period to draw from.
As it's non-Incabloc my watchmaker thinks it was manufactured between 1945 and 1950/52 based on his understanding that Incabloc would have been introduced in around 1952. If anyone on OF knows more about these specific chronos interested in building my knowledge.
I certainly like them now. Perhaps the name brand being so seldom seen one may still find these under priced for the value. Worth keeping an eye out for.