It was indeed the front office window of General Dynamics Allison Convair 440/580 ZK-PAL2 , c/n 501 . Known as "Joan The Jet Prop".
Below as VH-PAL at Timaru 01-01-2009.
Built in 1958 as a model 440 (with piston engines) and registered as N5123, followed by periods as N5122, C-GTTA and N631AR.
It arrived in NZ on 31-07-2003 and was registered to Pionair Adventures Ltd on 24-09-03.
Its NZ registration was cancelled on 14-09-09 to become VH-PAL on the 29th.
It has since returned to Canada to become C-GYXS from 21-09-09.