Vitro or Marble King

[Melissa]

I just stumbled  across a lot of these and I’m so confused with these types that look a lot like all red but could be marble king. Is there a trick to telling the difference?

[Ric]

Sometimes you can tell by the seams, patch traits, or colors, etc. but there can be so much variation within the different color combos from each maker that sometimes all you can really do is guess. As Ron always says - some just can't be identified with any real accuracy. The red/yellow and red/blue combos are probably the most difficult. From what I see here, only the top right looks like it might be MK - the others look like later Vitro production to me.