Must rosaries meet design requirments?

In order to be in keeping with all the traditions, apparitions, and history surrounding it, does the rosary have to be of a specific design? I know when it comes down to it, all you need is a way of keeping track of the prayers but I want to know if the indulgences and sacramental nature of the rosary require, for instance, Mary to be on the centerpiece or the crucifix to have a corpus.

I don’t think it matters, as to whats on the centrepiece etc. But it should be practical. Take a look at the following links. You might find them useful.
rosaryworks.com/custom0.cfm
ewtn.com/Devotionals/prayers/rosary/index.htm
web.cheapnet.it/ivanao/secret.html

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