OK, so here are even more photos that I took of an actual the gown I am trying to replicate.
This is a picture of the hem detail. They have simply turned up the hem, but haven't bothered to try to close up the hem. Given the level of detail in the rest of the garment,I have to assume that this was done for a reason. Must investigate what the reason is.
There are lots of small details to be considered because the robe has to help support and keep in place the hood. Here is a picture of the front of the hood and the front of the gown. There is a loop on the fron tof the hood which can be hooked around a hook in the front of the gown.
Here is a close-up on the top of the zipper:
There is a large hook and eye and a button with a large loop to accommodate the hood.
Also note that the velvet lining is part of the cover for the zipper. This picture is from the bottom of the zipper. It also looks as though the the velvet has been pick-stiched to the robe fabric, although it could have been the effect of the way I was holding it.
The last of the "fiddly bits" is the cord that extend from inside the neck. It comes down to a button and a loop. This is clearly so that the attachments on the hood can hook to it. The thing that confuses me is that I don't know what the cord down the back is doing. Is this just a bit of "fance" or is it because the velvet trim is only attached on one edge and the the cord helps hold down the trim in the back.
If anyone has one of these gowns and knows what this back cord is for and/or could be willing to take a picture of the inside back neck, I would appreciate it.