1. Open MSPaint - This is a free app that comes with Windows.
2. Use File Open and open stamp image Note; be sure to turn on the 'gridlines' under the View on toolbar.

3. Use Select tool (Home tab) as shown below

4. Select just the right hand side perf as shown below

5. Select 'Copy and then 'Paste' from the toolbar to place the right hand perfs next to the left hand perfs for comparison. You can move the selection around, be sure to align up the selection using the grid lines as shown.

This is the most basic way to compare perfs. Flat plate coils perfs should never perfectly align across. Let me know if you can follow the above.
Don