I second Jim on metal strings. As for specs, both my post-1881 Ceccherini and my 2004 Calace have a wee bit longer scale: 34 cm. the former, 33.5ish the latter. Regarding width at the nut, Jim's Romanesque Pandini may be a bit tight for my paws. For comparison, a modern Greek I have is 26 mm. at the nut veeeeeeery tight! The Ceccherini, a merciful 28 mm. My very, very comfortable de Meglio, 29 mm. I know of some (English?) mandolins that reach 30 mm., at which point one may be experiencing diminishing returns, i.e. a nut too wide to grip with comfort. I have no experience with that.
Still, metal strings are a given.
It is not man who lives, but his work. (Ioannis Kapodistrias)