What you may have John is the early Sealco plate that says push to park, and the valve has been changed to a newer style that is pull to park,a picture of nameplate and valve would be helpful.
Exactly what I was thinking.
I have an old Sealco parking brake valve from a White 3000 and it works as it's tag describes, but it is opposite of modern parking brake valves.
John just has a replacement valve and an old tag.
Grigg