Be sure your gun was made in 1926. Only lightweight 16 guages are called "sweet sixteens". Sweets did not come out until 1937 and Browning never made a 16ga magnum. Likely you have a standard weight Browning 16 guage. Your gun should be marked on the barrel OGDEN Utah if it was made in 1926. The chamber is 16ga 2 9/16. If you have a Sweet 16, the easiest way to check is the barrel ring. Take the forearm off and look at the ring that is welded to the barrel. If it has three holes drilled through, then it is a sweet 16 barrel. This doesnt mean the gun is a sweet. too hard to explain how to tell on the receiver. Scroll marking "sweet sixteen"on the legend began in 1948 /49 auto5man
Your browning sweet sixteen was made by FN for browning in 1926 with the serial number you provided.
Made in 1926.
1926, 100-1000 usd
1926
1926; 50-500 usd
This is not a serial number for a Sweet 16, but a Standard weight 16 ga. made in 1926. It's possible that there is a letter above or preceding the number which would identify it as a different gun than the one made in 1926.
Sweet Daddies - 1926 was released on: USA: 13 June 1926
Sweet Adeline - 1926 I was released on: USA: 14 January 1926
For about 40 USD you can get a history letter from Browning on your firearm. The sn you list does not follow normal convention. Just the numbers would date it to @1926.
This is not a serial number of a Sweet 16. If you have a Sweet 16, then there should be a letter and number above or a letter preceding the number. If these are the only numbers with no other letters, then you have a Standard weight 16 guage made in 1926.
If your serial number does not include and prefix numbers and letters,then with the serial number 43540 indicates that your browning Sweet sixteen shotgun was made in the year 1926.
Made @1926. Value depends on condition and exact configuration. Value range from a few hundred to multiple thousands of USD.