Here is the take down lever as it appears when removed from the grip. The two outer arms slant in and when pressed up the small, inner rounded buldges snap over the top edge of the grip frame. This holds the lever in the up, locked postion. The indentation in the center is where a steel pin that is snapped into the frame fits. The pins only purpose is to catch against the top of the recessed area which then keeps the part from being accidentally pulled all the way off the bottom of the grip. This is not of much consequence and the pin and recess could be deleted when fabricating a new part.
In this photo the take down lever is installed on the grip and is in the up/locked position. You can see that the small rounded bulged areas on the upper arms have snapped over the upper edges of the grip. This is necessary to hold the part in the up/locked position. This is a really old lever and both sides are exactly the same. The part is reversible and can be damaged if the shooter fails to fully lock the part in the up position before firing. The one pictures is damaged on the far side, so I reversed it. This part has been in the pistol for over 50,000 rounds.
In this photo the lever has been rocked back and forth to spread the top of the legs so that it can be pulled down in order to remove the slide. Note that the steel pin is now stopping further downward movement. If the pin were not there the part could simply be pulled all the way off of the grip. It is easy to remove and reinstall. The pin might help the part not get lost should it become lowered accidentally.
I'll put up some measurements soon. 1917