East Africa 1924 Silver 1 Shilling With Tone

Nice, most of the detail is still clear. I like the design on these coins.

I have a couple of the 1921 shillings - also with streaky toning and one with additional black "gunk" on it. As sel says it's the nature of the alloy that causes the usually unattractive surfaces.

The "East Africa" issuing authority is one of the few that released coins of Edward VIII

Dipping won't work in this case, they slowly re tone to this appearance.
You could cheat by dipping and rinsing very thorouhly, then adding an extremely thin layer of silver plating.
You just would not do this with a coin whose value is not justified.
Besides, the silver plating would be spotted a mile away!

I have had a silver florin gold plated for a fun exercise. Now, the gold plating seems to be amalgamating itself into the silver surface, and the coin is very slowly acquiring a paler appearance over the decades.
Perhaps you may bear this in mind if you want to cheat with a .250 silver coin. Just not worth it.

Eleventh Commandment: "Thou shalt not be found out."