The lower chain guide is made of a material and cross section similar to that which you describe.

When changing the timing chain, it is common and prudent to change the tensioner and upper chain guides sometimes the oiler also. The lower chain guide is often left unchanged for the following reasons; (1) Conventional wisdom believes that the lower guide wears at a much slower rate than the upper guide and (2) The cost of a chain job can double if the lower guides are replaced.

At 175k miles, you are seriously past due for chain service if it has never been done and/or approaching time for a second service if it has been done. Conventional wisdom again says about 90k miles between chain services for a stress-free driving experience.

My opinion is that it is time to get into the chain case. If you want to check further before committing, buy a lower chain guide (they are inexpensive) and compare it to your fragment to see if they match up. You could also take the fragment to an experienced, trusted mechanic. They should be able to identify it. I hope you still have it.