Seeing Clearly

I have a strict rule when it comes to windows: when windows reach their 172nd birthday, we replace them! Yes, you read that right, this apartment building was built in 1835, making it 172 years old. I must confess that I don't have anyway of knowing if these were the original windows, but they certainly appear to be. At any rate, the windows have now been replaced in two of the three upstairs apartments and I am planning to replace the windows in the third upstairs apartment by the end of the summer. My only problem may be finding more surplus windows of the correct size. I got the last 3 windows of this size at our local surplus store ($50 each), so I've got to find another source (or I'll have to pay retail). Retail and rentals don't go together!