Ray, in the early years guns without ejectors just had the "J" spring to hold the for-end on (ejector guns had a roller release that held the for-end on to the back end of the barrle's loop) From reports I had read there were complaints that in the field the for-end fell off and was lost, so Hunter Arms came up with the Curtis for-end release. This lasted from 1912 to approximately 1919. As you can see by the picture of the Curtis for-end there are a lot of parts and it took a lot of man hours to fit one. After 1919 Hunter Arms started putting the roller release on non ejector guns from Ideal Grade up and left the Field Grade (00 grade) on it's own merit by just using the "J" spring. The "J" spring held the for-end tight to the gun providing you did not try to put the for-end on with out first opening the gun to re-cock it. Doing it without re-cocking the gun you put a lot of tension of the "J" spring and after a while it bent, causing the for-end to be loose on the barrels. This is how many were lost in the field. Hunter Arms stated they stopped using it because of a patent infringement but in reality it was a cost factor. Putting the Curtis for-end on a 00 or Field Grade probably cost half the price of the gun. These were all hand fit and parts like the long push button rod were not interchangeable.
As to the workings, if you look at the picture, when you pushed the button on the end it opened the "C" clip at the end of the rod and this released it from the barrel loop. The barrel's loop had a groove machined in it to accept the "C" clip. Some collectors look for these guns with the Curtis for-end and you do not see many. They especially look nice on a Ideal Grade and up with the ebony tip with the button release in it.