I just posted pictures showing what the missing top support looks like. Great that yours still has the bottom bracket for it. This cabinet really needs the extra support for the table when it is open.
I was kind of wondering if the escutcheon on mine was original, but yours is exactly the same.
Did you get a key that fits? I've had a really hard time finding one so if you have one I'd love to get pictures with dimensions - it's a longer key than what you typically can find. And now days with the Steampunk craze, it's getting hard to find vintage keys - they are being made into jewelry.