In decision T 411/89 the board had to decide whether the amendment of a product-by-process claim from "obtained" to "obtainable" extended the protection conferred by the patent. The board took the view that the protection was not extended because the amendment did not modify the definition of the product which was claimed per se from the beginning and because the process used for its characterisation remained the same.
In decision T 423/89, by restricting the claim to only one of a number of manufacturing processes specified in the original claim and disclosed in the description, the patent proprietors had ceased to claim absolute product protection and had undertaken a significant limitation of their claim. There were therefore no objections under Art. 123(3) EPC 1973. The change in category from a product-by-process claim to a manufacturing process claim was also admissible in this case, as the protection afforded by the granted patent had to extend to all those methods of manufacture covered by the processes described in the claim and disclosed in the patent specification.
In T 20/94, however, objections under Art. 123(3) EPC 1973 led to the board's refusing a change from process claims to a product-by-process claim by way of amendment, as despite the fact that a product-by-process claim was characterized by the process for its preparation, it nevertheless belonged to the category of claim directed to a physical entity and was a claim directed to the product per se. The scope of protection conferred by a product claim exceeded the scope conferred by a process claim under Art. 64(2) EPC 1973.