Door Mounting Question

[Tedredamphi]

I'm getting ready to mount my doors on their hinges and have noticed a piece in the Amphicar manual and in Gordon Imports catalog called "strengthening piece" (11-36-5). The 3 bolts that fasten the door to each hinge apparently pass through this piece on the inside of the door. My car just had washers under each bolt head. I was wondering if these plates were used to repair loose doors or if they were installed in later years because there was a known problem with doors sagging or??
Can anybody shed some light on this for me.
Thanks,
Ted

 

[Canadian four amphs]

Some have them, some don't
they are a good thing and could easily be made(copyed)