Is This A Speciman Dime In A PL Pliofilm Package?

Why is one frosted and the other not? Did they mix the finishes in these pliofilm sets back in 1969? Kind of hard to see with the pic, but one is definately frosted while the other is not.

While I can't speak to why a certain date is frosted in Canadian coinage, (not my area of expertise) I can tell you how and why a proof or specimen coin gets frosted.

It is from the die being polished a certain way. the lower incuse recesses are not polished but often sandblasted, these are the higher points on the coin (opposite from the die) and the flat surface area is polished to a high shiny mirror surface. This is what leaves the frosty cameo look,which I particularly like on my proof coins from the USA. After so many strikings, the frost begins to fade, hence why there are various levels in the grading of the look, semi-prooflike, cameo, and deep cameo or ultra cameo (depending on the grading service). Proof coin are also using a specially prepared planchet (coin blank) usually washed and tumbled in steel bearing and oil to prevent corrosion and to help polish the blank previous to striking. Then the actual striking is often at a much higher tonnage and often struck multiple times to help build up the relief and make the strike stand out more than say coins struck for normal commerce.

In USA Proof sets you can often find a mix of frosted and just plain brilliant proof coins in the same package. It all depends on what the coins are like that come down the line at assembly time. Some years are known for all being well frosted while others are pretty difficult to find in a cameo or frosted look. Often in the much older (1800's era) coinage the normal strikes and also exhibit the frosted look and be quite deceiving as to whether or not they are proofs or regular business strikes. We see this on a lot of the Seated coinage in the USA from 1840's to 1890's.