A Parker #25L Jack Knife #fountainpen, originally with the "Lucky Curve" feeder, released for sale in 1919. This was a button filler made of ebonite from the early days of Parker before the 'Duofold' name was introduced.
One of the photos shows the same pen on a page from the 1919 Parker catalogue.
The catalogue page is from https://parkersheaffer.com/parker-pen-catalog-1919/