@FRENCHTRAINS Daniel what a wonderful find ! She is truly a majestic old girl , and so encouraging after all this time and neglect she will still turn over with air !
Normally I am personally 100% against restoration of old tinplate , but in cases like yours where there is no real visible trace of the manufacturers finish to be found , then the case for a restoration certainly has more weight , because you are not really replacing original with new , you are replacing "nothing" with something perhaps? It would probably be worth more to the general collectibles market if left untouched , but you will always find there is someone on the secondary market that likes "Pretty" ... I very much suspect tho that it will not be looking for a new home for a long long time , and that then says to me that whatever you choose to do is the right decision 
If it were mine I would leave it though ... but that speaks more about my crap restoration ability than anything else
