We know what a balance wheel is by now (if not, read this). But how does one make the necessary adjustments to this very essential component, the regulating organ, in a watch movement?
The featured image (courtesy H. Moser & Cie) is a blown up image of the balance wheel. As you can see there are little tiny screws on the balance wheel. That is one (haute horlogerie) way of finetuning the balance (poise) of the wheel.
However, that is certainly not the norm for most balance wheels out there. On mass produced and cheaper movements, you will likely not find any screws, the adjustments are instead made in a robotical fashion by laser etching. It’ll burn the balance wheel in just the right places to shave off just the right amount of material in order to get to the best possible balance. The difference between both methods is easy to spot as shown below: