I want to show you my new find and of course, ask for advices.
The keyboard is an IBM 4704 F77, I got it from a Bank that threw all the IBM stuff to the street. I only got this keyboard.

Gallery of photos: https://imgur.com/gallery/dizvviC
I was searching in the web and in this forum and I found that I can use an Arduino Pro Micro with the Hosu's firmware to make this keyboard work with usb interface.
Questions:
1) Is my idea of using an Arduino Pro Micro a good idea? In my country I can't get the teensy. And in the past, I made with the soarer's firmware a conversion to an IBM Bigfoot with an Arduino Pro Micro and the result was sucessful.
2) How rarer this keyboard is?
3) Can I get the buzzer work?
Regards
EDIT1:
I finished the keyboard's restoration, all the keys work well, but I have one problem to solve.
First, I show you the keyboard:



The problem is about the solenoid, when I connect the keyboard to the computer I hear a beep, but when I hit a key I don't hear anything. I tried to move the potentiometer to adjust the "volume" but nothing happens. I did a research, and I found that the Arduino must send a command to the controller in order to produce the beep when I hit a key.
Once the keyboard is completely finished I'll create a guide.
EDIT2:
DB-9 to USB adapter created!

Now I can use the amazing original cable and the buzzer works!
EDIT3:
As I promised, here is the post I created where I explain how to convert any IBM 4704 Keyboard with a cheap Arduino Pro Micro. Also, it has the solenoid fix! Enjoy!
viewtopic.php?f=2&t=22249
FINAL EDIT:
I want to share with you that the keyboard is in good working order, I use it everyday for programming!


I have one advice for you people, You must ENJOY your things, don't keep they in a shelf, use it!, make good things with they! Life is very short to see how things get rusty.
Thank you!!!