Grading UK Decimal Coins

hello there.
in order to give you an accurate answer, I have to know the years of the coin sets and the specific coins you are concerned about.
For 50p coins, cameo-like colour difference is not a major problem since sooner or later, the alloy that is used on those coins get a little bit darkened, no matter what you do. I have experienced this with 50p coins from year 2000 and above. Suprisingly, pre-2000 50p coins don't get darkened. possibly a subject of reserch I guess. Perhaps the copper quality, who knows.

Coinas inside mint-packaged sets are almost 100 percent problem free, if we are talking about UK mint. Those guys out there knows their "biz" I assume. For 10p coins, check the feathers of the lion, that is the highest point. for 50p check the hand that holds the trident. That is the highest ponit as well. 1 Pound coins all have different designs so I can say checking the hair of ole' Liz on the reverse does a good job. 20p coins are so far, the most resistant coins in circulation, for them you have to check the bust again, the other side doesn't get affacted very much in circulation, due to the cartwheel design. Ask specific coins if you can and I will help but don't worry a lot about coins inside mint packages, they're all Uncriculated, and do not worry too much about the lustre. Even proof coins get a little bit cameo toned over time.