Unfortunately with the exception of Gerber Center Drive/Center Drive Plus, none of the other multi tools offered by Gerber are 100% USA made anymore. Sure some models do have USA made components, but only the multi tools currently listed under Gerber's American manufacturing website. Determining which components are American made and what aren't isn't often listed, but if I had to guess the USA assembled with some domestic component multi tools, the knives are probably USA made. As of 2019, only the MP400, MP600, including Pro Scout/Bladeless, MP800 still have USA components. After calling Gerber, I learned that the MP1 series has been discontinued in 2019 sometime.
Simonds, the file company Gerber contracted with for a while, hasn't made any domestic files in well over a decade sadly. Then again, to my knowledge, there hasn't been a hand file made in USA after Nicholson offshored labor years ago as well. I've managed to locate some specific product images that confirm my statements.
First Gerber MP450.
As of 2016, based off the date on the cardboard packaging and this unit is now discontinued (2017/2018 is when this was discontinued I am guessing), the MP450 was assembled in USA with USA and Taiwan components. Not surprising, the sheaths were made in China.
Second is the Gerber MP400. Still in production and I bought one in 2019. There are two finishes, but the origin is one of the same.
This is assembled here and has some USA components. This package (2016?) merely lists "global components", but what I bought listed USA and Taiwan. My guess is the knife is USA, jaws/scissors are made in Taiwan, but I have no idea about the slotted driver and Phillips though.
Gerber MP1, which has been discontinued in 2019.
MP1 and I am willing to bet the MP1 Maintenance Pro are one in the same are assembled in USA with components from USA, Taiwan and China. Personally the MP1 Maintenance Pro is one of my favorite multi tool's due to the prybar, knife design(s) and the locking system. Decent wire cutters within reason.
Gerber MP600. With the models with the carbide cutters, the replacement teeth are USA made. Not sure about the screws/Torx wrench though.
While similar to the Gerber MP400, this is assembled in USA with USA, Taiwanese and Chinese components. Similar to MP400, these used to be stamped USA, but due to the FTC regulations, because there is foreign components, albeit I am not personally sure of the percentage, the USA engraving is gone.
Gerber Legend MP800.
While this unit is still in production according to the Gerber representative, despite the packaging being slighter older potentially, this unit is still assembled in USA with USA components.
In 2016, Gerber released the Center Drive and is stamped made in USA. With some models, this unit comes with a USA made leather sheath.
2019 was when the Center Drive Plus came out. This unit has scissors and a different knife design. Still made in USA and the model I bought came with a USA made leather sheath.
J-Sews is correct, the Gerber Clutch is made in China.
Gerber Balance, according to Blade Head Quarters is made in China. This has been discontinued, not sure of the date.
Gerber Crucial, still in production as of 2019.
BladeHQ is a source of some information, albeit some of their information may not be 100% correct. Case by case and this is challenging with discontinued items though.
Gerber Evo. Made in China. Still in production as of 2019.
Gerber Steady. Made in China. Discontinued and has been for a couple of years I am guessing.