Help With Brazil Coins

Hi,
I'm asking an help related to 1970 Brazil coins.
Does somebody know if there are differences types or varieties in 10, 20 and 50 Centavos minted from Brazil in 1970 ?
This question because I got from an auction a Brazil coins collection, about 300 coins, no one double from early 1800 up to late 1900, of couse some types or date missing.
But 10 and 50 Centavos 1970 are double and 20 Centavos 1970 are triple, so why I think there are differences I don't know and I'm not able to see, I already checked on Krause w/o success.

below pictures of 3 copies of 20 Ctentavos 1970.

Thanks a lot, Antonio.

Image: 20Centavos1970Obv.GIF
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Image: 20Centavos1970Rev.GIF
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