H&K VP70 the first polymer-framed pistol produced. The pistol, chambered in 9x19, was produced in 1970 but it didn't sell very well. It had, among other things, a nasty trigger pull (about 18#). The pistol was however capable of firing in burst (3 rounds) with the attachment of a special stock (which also served as a holster). This picture shows how the stock attaches to the VP70M. Note that the 1-shot / 3-shot selector is on the stock, not on the pistol. You can see the selector just to the right of the slide.
Thanks to Cal