As some have already stated.
The gun was reproofed at sometime. Perhaps more than once.
The *AE and *AD are old Controller of proof marks, pre-1924. The proof house in Liege has stated the documentation for these early marks has been lost.
Please understand, the Controller never touched a gun. He ran the proof house.
The date stamp f is 1927. The chambers are 12 ga 2.5" It is smokeless proofed, NOT for current ammunition pressures. The bore is 18.5 mm. The gun is choked, but they stopped giving the dimensions for the choke after 1924.
The numbers up on the barrel 1.??? is the weight of the barrels in kilograms at the time of proof.
The AD on the rib is Alexandre Dupont. He may have only supplied the barrels. The 4 is just a factory batch number.
It would help to show pictures of the entire gun.
You did good in reading the proof marks by the way. It takes looking at a lot of guns to discern all the Belgian marks.
http://damascus-barrels.com/Belgian_Trade_Marks.htmlhttp://damascus-barrels.com/Belgian_All_Proofmarks.htmlPete