1 Krona Sweden 1968 U [opgelost]

Hello dear fellow collectors and Sweden specialists.
I have problems to distinguish:
1 Krona Sweden 1968 U (SIlver 400, KM # 826)
and
1 Krona Sweden 1968 U (Copper-Nickel plated Copper, KM # 826a)

Is there only the thickness as difference? (1.78mm vs 1.84mm)
Even with a caliper I have difficulties to determine, because the coins are sometimes very worn.
(Ok ... my caliper is old and worn too ;-))

Can anyone give me a hint please? Many Thanks !

I don’t know if the edge could be helpful depending on the process how those coins were made it could show the copper core. Other than that, the thickness would be the easiest solution also new digital calipers are quite cheap.
The toilet paper method was sometimes of help, you take toilet paper if multiple plies take it apart until you have a single thin layer of paper and look at the coin through the paper when it is still white silvery it's silver when it's dark it's Cu-Ni. Don't know how well this works with low percentage silver.

I suggest you to make silver tests. You can find many posts regarding those tests. Ping test, with resonance frequency, is my favorite.

Thanks for all hints, there is so much i can still learn here.

The ping test works surprisingly good. Even though its only .400 Silver the difference is so clear. Lucky me i got one coin of each kind

Olli - you nailed it !