According to the chicken calculator, the parent stock could indeed make this hen. That cross (RIR over SLW) is indeed a sex link cross, pullets red and cockerels silver. Calculator says the lacing would be incomplete, and I agree this girl's does look pretty good, but it's apparently possible.
You'll just have to take the seller's word on the rest of it, especially if the parent stock are hatchery birds. If they'd been SOP birds, you'd be able to see the mixed body type easily, but hatchery birds all look so close it's impossible to identify a cross like this from body shape alone. Comb is no help, as rose comb is expected to be dominant over straight, and both parent breeds have yellow legs so that's also no help.
As far as lacing, I had this cockerel who was a bsl rooster over a GLW hen, he had pretty decent lacing for a juvenile (I never got an older picture of him), and for a cockerel at that...
You'll just have to take the seller's word on the rest of it, especially if the parent stock are hatchery birds. If they'd been SOP birds, you'd be able to see the mixed body type easily, but hatchery birds all look so close it's impossible to identify a cross like this from body shape alone. Comb is no help, as rose comb is expected to be dominant over straight, and both parent breeds have yellow legs so that's also no help.
As far as lacing, I had this cockerel who was a bsl rooster over a GLW hen, he had pretty decent lacing for a juvenile (I never got an older picture of him), and for a cockerel at that...