Obvious? no. That's why I asked.
Your subject line asks specificially "Is the G&B lamb about the
strongest version of that hide?", then open the thread with "curious if anyone has
weighed one of these jackets size 42 or over to find out what it weighs?"
Those are two different questions. Are you asking about weight, or strength? One does not necessarily equate to the other.
Tannieries refer to 'tensile strength' guidelines set down by the tanning industy to determine strength of a hide for making items like garments. They then use a calculation to determine how thin to shave a hide regarding physical weight of an item. One is not necessarily set for the other. A thick lambskin will still have the same tensile strength of a thin hide.*
You answered your questions yourself, "Like any leather, how it is treated and tanned will make a difference."
For example, I've owned several lambskin Wested jackets over the years. One is still in the possession of my eldest daughter and dates back to 1998. It's tough as nails, and STILL working hard. Looks like heck, but then it's been used and keeps on coming back for more. I then had one that literally fell apart on me within a month of receiving it. Snagged and tore on anything it touched.
Same company, and supposedly the same material...but apparently one was tanned a lot better than the other, and probably by a different tannery using a different tanning method.
If you're asking about continuity in tanning, I'd vote for the G&B myself.
Every one of them that I've examined over the years have appeared to be finished exactly the same, though like any lambskin, not anything I'd want to have to depend on to protect my hide if I fell out of a car....but you won't have to worry about the seams breaking.
Regards! Michaelson
*
Source material acquired from speaking to the head leather tanner at the "Tennessee Tanning Co., Tullahoma, Tennessee"