Old roth Query

All these vases were made by roth keramik , a company not know for giving out any information about its products from the 1970's 80's ,
I have no qualms about all the very commendable research that has gone into IDing these pieces, however some things just don't add up ,
The chimney vase, the big red and black lava vase and the two handled orange vase were made by the same company , no doubts that's 100% guaranteed , so what's the problem , ? why has there never been roth labels found on these vases ,unlike the orange vase with the OO handle , this type often has labels ,also the three first mentioned all have impressed 4 figure numbers , the labeled types are moulded 3 figure with W.Germany .