There must be lots of ole-school fixed-width machines, which have stack machine built-in. Especially if you decide that top-of-stack means contents of the accumulator(s). To make it a "forth", you need separate string space, where machine words are linked to symbols. 1+ for example is just INC.
Many modern RISC architectures have pre-increment and post-decrement addressing modes for all their general-purpose registers, so it's very easy and convenient to maintain multiple stacks and implement "NEXT".
