<VV> Fw: `66 Defroster Valve Repair

[John Howell]

I am reworking the heater duct system in my `66 Corsa. The defroster valve ( per shop manual ) had some type of rubber seal affixed by metal staples to the little metal door ( located in duct at center of front floor board )  operated by the defrost control. The rubber has long since rotted away and there is nothing left to get a measurement from and checking other late model cars show the same problem.
Can anyone give me the measurements of this piece of rubber so I can replace it ?  Or any other helpful information on this repair ?

Thanks  
John Howell