Excuse my ignorance but where did you get these? I've been doing some searching and I'm finding out their a hybrid of some sort?
One source says they put a Chocolate Orpington roo over Lavender Marans hen but that's about as far as I got, other than a thread here on BYC I haven't read all the...
I might not be much help but I just use colored zipties on my Marans. Haven't lost one yet but I have had to replace them as their legs grow.
They sell different width/thickness also.
Very pretty girls you have... 🙂
Edited to add pic.. she has 2 red zipties.