Hi Bill
Yes I totally agree with you. What happens is that when the Tamiya's appeared I believed that non of the M51 used radials. I was so focused in the more known ones so I forgot to reserach the matter. Now with all the leftover parts I was back to the books and realized that they had all radials in the beginning as you say.

I call this prototype just because I'm building it with leftover parts, I really don't know if they had a prototype but I guess could it be probably, who knows with IDF.

It's a low cost models ( I spent US$100) and the parts had not much value selling them separately so did I said why not?

Thanks for all the information, appreciated!