Walter doesn't question whether or not the woman has hands - instead, and more realistically, he wonders whether or not her arms are tattooed, and whether she'd just prefer to keep that private.

"Longer than Nanny Ogg, perchance?"

Give him a timeframe to work from, here.

Walter keeps his tone light, genial.

"They're very well-made," he compliments - meaning it, even though he did find several of the designs... odd.

"You don't have dormice around working as models, do you?"

It's said in a joking tone, but also a genuine question, a testing of the waters as it were.