I started writing this thinking it was a different stick, then realized that I've already posted images (https://nfggames.com/forum2/index.php?topic=6286.0) of the RAP V, so... consider this an Inside Look Gaiden post.
Hori's Real Arcade Pro (RAP) V is a great joystick. It's well made, but has a cable compartment cover that is very easy to break (see: 3D printed hinge replacement (https://nfggames.com/forum2/index.php?topic=7313.0)).
Anyway this is what it looks like inside:
Hori-RAPV-Inside-1.jpg
Fairly standard construction for Hori. A plastic shell with a metal top panel screwed to it.
Hori-RAPV-Inside-3.jpg
The buttons are Hori's Hayabusa / Kuro. They use a 110 faston connector, same as most Japanese arcade buttons.
Hori-RAPV-Inside-7.jpg Hori-RAPV-Inside-2.jpg Hori-RAPV-Inside-4.jpg
The main logic board is very small, with a glop-top chip, and four cables running to the touch panel, the side mounted controls and the USB cable.
Hori-RAPV-Inside-5.jpg
The USB cable has a massive ferrite choke on it to reduce interference.
Hori-RAPV-Inside-6.jpg
The joystick mechanism is Hori's own Hayabusa stick, which uses a Sanwa compatible pattern to mount to the plate, which in turn uses a Vewlix-style pattern, as many modern sticks do.
(http://nfgworld.com/grafx/games/hardware/Hori-2.jpg)
👆 Vewlix mounting pattern
(http://nfgworld.com/grafx/games/hardware/Hori-3.jpg)
👆 Sanwa JLF/JLX compatible mounting pattern
The stick uses a square gate, and I definitely recommend the Kowal octogate (https://www.cqbarcade.com/products/kowal-hayabusa-octopus-octagonal-restrictor-plate) as an upgrade.
(http://nfgworld.com/grafx/games/hardware/Hori-4.jpg)