What kind of latch is this?

[confundida]

I wanted to change the latch that was sticking on an internal door. The latch is bigger than I expected (case width 40mm) and doesn't look like the usual type of latch I've seen before. Does anyone know what this type is? It seems to have odd measurements as well (approx 83mm case, 62mm backset). Any ideas where I could find a replacement for it? Thanks.

 

[Notch7]

mostly superceded by tubular latches

what you have is described as a flat mortice latch

this one is pretty close to your size

Legge 3709LK - Flat Pattern Latch (76mm)