The rule was you had to use shells purchased when you paid your entry fee. They had to come from the shell house on the grounds. The rule changed only once to my knowledge. The shells were not marked. In later years the companies did make special runs for the Grand.
IF you ejected the hulls, they became the property of the club. Many trap clubs had this rule, but not all. The shells were sorted by the trap boys and sold to the club members for a nominal fee.
Back in the day, the saving of shells while shooting the trap line was considered a distraction. Most shooters used their ejectors in registered competition. Not all, as can be seen by watching the movie.
As far as automatics at trap, apparently you've never heard of the Remington 1100.
Many, many, very fine trap shooters used 1100's. In fact, that reasonably priced product did more to popularize the sport than any before or since. You had to carry spare parts, but you were in the game for a couple hundred bucks.
ATA blundered badly moving to Illinois. It is indefensible and unexplainable.
Not to disagree with you Shotgun, but if you look at the movie, I don't see that many automatic shotguns. If any. And very few single barreled guns. I would say about 80% of the guns are Model 12s. They ruled the trap world though the 40s, 50s and even the 60s. And you sure as heck won't see any 1100s in that movie, because they weren't even made until 1963. By then, Winchester Model 12s came to a slow down because they started stamping out parts and people got mad and quit buying them. Have you ever heard the term- "pre-64"? So no gun even came close to competing with the Model 12 during their time. By then people started using 1100s, but that was an entirely different era. And they didn't last that long because the single barreled trap guns had come along and have been popular ever since. And if I can post them, the shells in the 2000s had ATA Grand American stamped with the date right on them. That way they would know shooters were using their shells. I don't know, but, did anyone ever win the Grand American with a 1100? Other than a few classes? I guarantee you, not like the Model 12s did. The Model 12 was considered to be the most natural pointer ever made by a lot of people. Al Ljutic designed the Ljutic trap gun after the Model 12. So, in their day, Model 12s ruled the trap world. No automatic came even close.