I spent the last 20 minutes or so scanning a few brick collector websites, but had no luck in identifying the manufacturer and range of dates during which these bricks might have been manufactured. Unfortunately, just in Ohio alone there have been more than 2,300 brickmakers over the past 200 years, and I have not been able to locate a definitive encyclopedia or Web reference dedicated to American brick makers with images useful in identification. The wear and erosion on the brick reminds me of the sort of wear I would expect to see on a late-19th century building, but of course I am not an sort of expert in determining the age of a piece of masonry.
Thus, I throw my brick query to the Internet: if you can identify the manufacturer, or if you have better suggestions on identifying these bricks, feel free to post your thoughts in the Comments section. What I find amazing on a needle-in-haystack post like this is that someone, somewhere, and sometime will have the same question and will wind up on this post via Google.