Faux tortoise shell how to question

Ok so I cleaned up a couple of str8's a 5/8 W&B and a 4/8 Kraut & Dohnal in my collection that had a faux tortoise shell finish on the scales
it actually looked like a dark varnish or something was dribbled over the light horn.

which due to the amount of sanding required to clean them up has removed most to all of the effect on them

my question is does anyone know how this effect was made or done it themselves as I would like to try and replace it if possible

1 before photo then each side after
thanks for any advice in advance
cheers
D

Neil is probably the most knowledgeable about how some of the old scales were done.. My understanding was the pattern was done with a stain while they were being pressed into shape when the horn is in a hot malleable state... I could be wrong there, maybe Neil knows for sure