If you are looking to pick up a new shotgun, I believe all the currently manufactured 686/687 28 gauge shotguns are on the baby frame. Which would be the Silver Pigeon I, the Silver Pigeon III, the Silver Pigeon V, and the 687 EELL Diamond Pigeon.
If you find a nice used one, I can give up this from Beretta's Customer Service, dated 3/13/2007, and I quote:
"Which models are now built on the 28 gauge frame instead of the old 20 gauge frame?"
"As of 2005 the small 28/410 gauge frame is offered on the following models that are sold with 28 or 410 gauge barrels.
686 Silver Pigeon S (2005+ up models)
687 Silver Pigeon III (2005+ up models)
687 Silver Pigeon V (2004+ up models)
687 Gold Pigeon II EL (always on small frame)
687 Diamond Pigeon EELL (always on small frame)
The small frame can also be identified by measuring the overall height of the receiver (from top to bottom) in the area just in front of the top lever but behind the breech face. This measurement should be equal to 2 inches."
Another Beretta Customer Support FAQ also adds the 686 Covey to the list of baby frame 28 gauges. But, MY Covey is not a baby frame, but then there were two versions of the Covey, which may explain that discrepancy.
Notice that the Silver Pigeon I is not on that list of baby frames. That is because they weren't manufactured until 2011. They are all baby frames.
A note on the 2 inch measurement of the baby frames. Maybe I'm doing it wrong, but my baby frames measure approximately 2.1" in that dimension, and my 28's on the 20 gauge frame measure about 2.2".
