Why would I want to install Bryce 4.0? After all, I have 6.1.

I have my original copy of 4.0 with a great PRINTED manual, remember those? and the equally great book "Real World Bryce 4 by Susan Kitchens". I would like to install the program on an older computer for my grandson and feel that having the written material available would be a great help.

 I have a problem, however, I don't have my serial number. I have everything except the original CD case which had the number on it.

I know that 5 is free. Would the 4 manual and book be close enough to be useful?

Does anyone have a suggestion or perhaps a number for me so that I might install the program?
TIA
Jim Barbieri