Old Yatagan

[gp]

Originally Posted by SchwarzStock

The handle appears to be horn. Any suggestions on cleaning? I was thinking just a stiff brush and soapy water....

I would start with either vaseline or a colorless natural oil ( nuts or virgin olive oil is also OK) on both blade and handle.
This will loosen any dirt or corrosion and also feed the handle which sometimes became too dry. The latter will avoid it to split. Repeat it if the handle is too dry.
Let it work for some time; subject to the dirt, either a couple of hours or a day.
Gently rub with a piece of cloth, cotton is OK, the dirt off.
Next I use aceton on a piece of cotton cloth to further clean the blade.
Once done, if needed you can finish with some very fine steel wool.
To polish, use a gum ( best tip ever, thnx to Detlef !) on the blade and silver or gold decoration. This will show its beauty.
Last but not least, apply either some specialized conservation wax or vaseline, colorless oil to leave a small thin protective layer. Good luck !
It worked for all my yataghans and bichaqs. And they were as dirty, two even more, than yours and below is the result