ARVN Engineer question

I have yet to find a correct ARVN order of battle.

Here I have two engineer patches referred to as "40th Engineer Group"



The designs are obviously different.
Is it the same unit?
Is it the same time frame?
Is there one Combat Engineer Unit, and one Construction Engineer Unit maybe?

I also have this one, which appears in the 1971 ARVN book:

Is this a later variation of the castle design?

And why are the colors inverted?

The shield is that of 40 Engineer Group; the pentagon is the badge of 40 Engineer Base Depot. They're different units. I'll post more soon.

HTH

RW

As promised; more on ARVN engineer insignia. Shoulder patches exist for all the following...
40 Engineer Base Depot Saigon/ Can Cu 40 Yem Tro Cong Binh
41 Engineer Support Battalion/ Tieu Doan 41 Yem Tro Cong Binh
42 Engineer Support Battalion
43 Engineer Support Battalion
44 Engineer Support Battalion
45 Engineer Support Battalion
10 Engineer Combat Group/ Lien Doan 10 Cong Binh Chien Dau
20 Engineer Combat Group
30 Engineer Combat Group
40 Engineer Combat Group
5 Engineer Construction Group/ Lien Doan 5 Cong Binh Kien Tao
6 Engineer Construction Group
7 Engineer Construction Group
8 Engineer Construction Group
1 Engineer Topo Group/ Lien Doi 1 Dia Hinh

The early patches for the combat groups were red and green with a black bulldozer, this was changed to yellow and green with a red bulldozer before changing again to show the pagoda. The construction groups only used green and yellow patches with the bulldozer or pagoda and the support battalions only ever used the pagoda.

The other pentagonal badge is that of the Buildings and Construction Directorate.

This seems to make perfect sense; thanks Rolfi!

Great info ! Thanks Rolfi.