The 16 ga. Auto-5 was introduced in 1909. In 1936 Browning introduced a lighter version of the 16 ga Auto-5 and called it the Sweet Sixteen. Starting in 1948 the words Sweet Sixteen were engraved on the left side of the reciever. The standard sixteen stayed in production till the early 60's, while the Sweet version was made right through the end of A5 production.
The weight reduction was accomplished through extensive extra machining inside the reciever, drilling lightening holes in the barrel ring and through use of a narrower rib on ribbed barrels.
The weight savings ranged a bit, depending on wood density. It was typically around 8 oz but could be as much as 10. In addition to weight loss the changes affected balance and the Sweets are very fast handling guns and a delight to shoot at fast moving game like wild quail or ruffed grouse.
Many people refer to thier standard 16 ga Auto-5's as Sweet Sixteens but they are not correct, it is a substantially different gun. The standard guns are great guns, but they are not as highly valued as the "Sweets".
Jeff
ps:
1) there is no such thing as a long tang A5, all of these guns had the same length tang.
2) until production resumed after WW2 all 16 ga Auto-5's were made with 2 9/16" chambers and will not cycle standard modern 2 3/4" shells. Some of the short chambered guns were modified to take the longer shells and it pays to know how to tell tham all apart if your looking at older Auto-5's.