I have a thing for vintage water decals. Meyercord is a common maker and they come in a huge variety of styles. I found a big stash of them the other day at an estate sale. (I already had some, but now I have more!)
Vintage water decals can be tricky. To apply them you soak them in warm water for a minute or so and then they are supposed to slide off the cardboard backing onto the item the decal is going to be placed on. I often spray mine with varnish prior to soaking them in water. Let the varnish dry before soaking. I have had good luck with the varnish holding the decal together (most of the time).
This little lamb still came apart (his nose) when I applied him.
After the decal is in position I lightly dab away the excess water with a paper towel and make sure there are no air bubbles. You can use your fingers to smooth out the image. Let the decal air dry.
Here are a couple of tiny decals soaking in water waiting to be applied.
I have not found a test to see if a decal will stay together or not. Often the larger decals tend to break apart easier. This tiny decal simply disintegrated when I tried to remove her after soaking. I did not spray her first with varnish and that might have saved her.
These water decals are addictive! I want no more naked jars in my studio.