Some answers:
There was no such rank as "Lance Corporal"; this was an appointment awarded to soldiers holding the rank of Private.
At the time of unification, the Lance Corporal appointment, as well as the Lance Sergeant appointment, were abolished (a Lance Sergeant was a corporal who wore three chevrons). Staff sergeants were replaced by the new grade of Warrant Officer, with MWO and CWO added. The old system had only two grades of warrant officer - WO II and WO I. (In WW II, there was a third grade, called WO III who usually acted as Platoon Sergeant Major - this rank existed only briefly in 1939-40 but remained on the books throughout the war, and was abolished either during the war or not long after).
The new CF rank structure included a corporal and the appointment of Master Corporal. There was also some weird kind of "career corporal" grade.
The initial insignia included a leaf on top of the chevrons for trained privates and corporals and over the chevrons for master corporals.
Some feel that the master corporal appointment completely destroyed the junior leadership ranks; a Corporal in the old army was a command position equal to a sergeant in the US forces. Today, it is a gimme rank - and privates, trained privates, and corporals are all roughly equal to each other in terms of responsibilities - much like the German Army of WWII, where Schutzen, Gefreiten, and Ober/Stabsgefreiten were all glorified privates.
The crown and chevron insignia appears to have been used by corporals - not just staff sergeants - perhaps as an interim until the new insignia could be issued?
There is some info on rank insignia at
www.canadiansoldiers.com and a forum you can talk to some insignia experts at - also one of the regulars is a Canadian Military Engineer and can probably answer many of the questions you have about your dad.
