I got this from a job lot. Initially, I thought "With that Wheat engraving, it's probably a Keystone". But the straight back with Nib and the tote says it's too early for them; and the tote looks like Apple, rather than Beech. And the medallion is a proper Disston 'Philada' 1896-1917. The sawscrew positions say it's the old style "pre-D" – same as 7, 8, 12, 112; but the 7 and 8 don't have Wheat chip-carving, and the 12 and 112 have the extra thumb-hole ahead of the lower limb - which this one doesn't. The positions are similar to other early 99s; but the rear top screw on them is lower. The domed-nut screws say "post-1887": but the Lamb's Tongue and dog-leg shape of the lower limb suggest earlier. The curve at the heel of the plate suggests either 12/112 or 99. My best guess is that it's a late C19 Nº 99, from a period when the tote changed more than once. But what do the experts say?