Maybe this is related to what you were saying- This is what I was thinking of when i said the silver gene, I didn't know the exact phrase until I saw something today about it with silkies.
Couldn't these guys be silver based white?
Yes, I will list all the genotypes I can think of to produce a white phenoytype:
Recessive white:
c/c + anything else
Typical Dom white:
E/(any E locus), I/I
White Silver Birchen:
E^R/ E^R, I/I, S/S
White Silver Wheaten ???: E^Wh/E^Wh, I/I, S/S
White Silver Partridge:
e^b/ e^b, I/I, S/S
White Silver Duckwing:
e+/e+, I/I, S/S
Melanised White gold(en) birchen:
E^R/ E^R, I/I, s/(S or s), Ml/Ml And/Or cha/cha
White Silver Columbian
White Silver Pencilled
White Silver Laced
White Silver Double-laced
White Silver Spangled
White Silver transverse pencilled
Silver “Buff” ??? (As in Silver/light columbian with Db/Db)
Any of the above with mottling
Any of the above with barring (could also be ‘ghost barred’ rather than pure white)
Any of the above with any Black dilution (blue/splash, chocolate, lavender, etc)
Any version of the above with any recessive genes that do not affect phenotype when heterozygous change phenotype
(silver only appears white if no autosomal red is present)
??? = I can’t find/ have never seen an example but it would presumably be white.
This message is really just to show how many genotypes are responsible for one phenotype. Most pure bred show birds will be either of the first two options, but many mixed breeds or pure bred colours bred from other colours can have all sorts going on that only breeding reveals.