Decals on decals?

Yes you could, another Gloss coat would not needed, just make sure 1st decal is dry.You can add some set to the 2nd decal.

I agree with Tojo72. Recently had to cover a less than good marking with another on top and had very acceptable results.

Thanks fellas. Helps a lot

Several decal makers used to make layered decals.  It required a less complex silk-screen process, one decal for each color.  A lot more work for the modeler, cheaper for the mfgr.  One popular one was for car models, where gloss coats were usually  only done as a final coat over finished model.