The FROG 100 of mid 1947 was the first diesel model to appear as a member of the early FROG "bicycle spoke" series of British-made model engines. The manufacturers of the FROG range, International Model Aircraft (IMA) Ltd. of Merton in South London, England released a series of these unique designs over a four-year period beginning in early 1946. The first model was the 175 spark ignition unit, which was followed by diesels in both the 1 cc and 1.8 cc displacement categories as well as a glow-plug model of 1.66 cc. All of these models were constructed to a common basic design. Although becoming increasingly antiquated in style as time went by, these dependable little engines survived in production until 1950, when their replacement by more up-to-date designs commenced. For the complete story of these highly individualistic powerplants, see the detailed article to be found elsewhere on this web-site.