B17 parts question

[SPANNERmkV]

The TEXAS RAIDERS parts pile has offered up a couple of good STUMP the warbirds guys questions.
First

B17 Rear Gunner's escape hatches.
We have two variants. The outside and the hinges are the same.
But the inner framework is WAY different.
The Douglas Built B17G -TEXAS RAIDERS has the boxier inner frame hanging on it presently.
Does anybody know what model or manufacturer used the stamped style?

Pictures being worth a bunch of words- HERE GOES another stab at Photobucketing.

[bdk]

My guess is that the stamped one was made later as a time saver for manufacturing. I have no direct knowledge though.

[hang the expense]

For what it is worth BDK would be right. Lot less parts and riviting. Later nose hatches are also a stamping whereas the early birds(D,E and early F are built up doors.

[bdk]

Is the stamped unit riveted or spot welded together?

[hang the expense]

Fom what I have seen some areas are rivited to set the parts and then the rest is spot welded speeding up assembly on late models.

[REGINALD VON GLEASON III]

the inner framework was a result of the refranastatic "zip" weld...a new technique, thought to be groundbreaking at the time, however, like most wartime magic bullet time saving proceedures, proved one thing indeed. Too costly. This factoid provided by an uncle, employed at the time at the Martin plant.