Oh gosh,
That is a tough one. The model 100 was introduced in the 50's, in 1959 the 470 was introduced. My guess and it is only a guess is it probably would fall somewhere in between. You might e-mail a friend of mine who could get closer. Her address is <!-- e --><a href="mailto:sherry@oliverinformation.com">sherry@oliverinformation.com</a><!-- e -->
Have a great day!!!
Andy