Upvote:4
This is a placeholder for an answer. This is definitely a Polish uniform. The cap shape and collar decoration are distinctively Polish. The cut of the uniform looks World War I-ish. I don't think the Sam Browne belt was much used outside Britain until about 1910, and became extremely widespread after World War I.
The Wikipedia article on Sam Browne belts has a photo of a modern Polish officer wearing the same kind of cap as your relative, with a zig-zag decoration on his cap related to the wiggly collar decoration on your photo (as discussed here; that discussion cites this), and of course sporting a Sam Browne. The first two of these three things are definitely Polish.
Since Poland was not an independent country in the period 1795-1918, without an army of its own, it is unlikely your photograph dates from before 1918. I believe during World War I there was a Polish Legion fighting with the Germans against Russia and a Blue Army fighting with the Allies against the Germans. After the war veterans of the Blue Army wore a uniform similar to yours, even though during the war itself the Blue Army uniforms did not look like yours.
If the writing on the breast-pocket badge says "CzoΕgi" [="tanks"] as Spencer commented, the likelihood is that this was a Polish uniform of the period 1918-1939. The Polish Army made extensive use of tanks throughout the interwar period, as described in this Wikipedia article.