I recently took possession of a rather nice four panel Irvin, which IMO dates to late 1940. It has the Crown and AM on the zip pulls, which was only stamped on zip pulls from this period onwards. The jacket is a size 5 and I love the almost copper coloured fleece. It has had very little wear.
I have long been interested in the differences between the "house" features of different makers. Wareing and Co invariably used large collar rings, and wide belt loops for example. Links used rounded collars whilst Irvin Air Chute had squarer collars. Here are some pictures of my 1938 and 1940 Irvins. The 1938 jacket is the work of Irvin Air Chute. The 1940 jacket is the work of DGL.
1938 view of collar rings and construction of the leather loop.
1940 jacket has larger rings and a very different style of fixing the collar ring loop to the collar.
1938 Irvin's slider bucket is marked "Dot British" and has conventional sized rivet heads.
On the 1940 jacket the slider bucket is marked "Dot made in England" and it has over large rivet heads.
Notice the pattern of the 8 ventilation rings on the 1940 Ivin.
Now the 1938 Irvin
Buckle on the 1938 Irvin
And on the 1940 jacket.
Both jackets together, with the 1940 on top.
1938 Irvin.