This is the later, plastic gripped, variant of the Diana (Milbro) Mod 2. The air pistol was also known as the Diana G2 or Milbro G2 according to advertisements and packaging. They were manufactured by Milbro from about 1965 to 1982 and were available in blued or nickel-plated finishes. There were two sub-variants of this air pistol. The earlier sub-variant used the same action as the wooden gripped Mod 2. In that sub-variant, the front half of the body is distinctly narrower compared to the later sub-variant of the plastic gripped Mod 2.
The pinseal may also be different from one pistol to another. The later variant pinseals are normally cylindrical and knurled whereas the early variant may have a traditional ornate shaped pinseal. It is also not unusual to find the early sub-variant with the cylindrical type pinseal.
Until next time, happy shooting!