Jordan Windows balancer

Thanks for writing in. This does look like a Series 390 balance. Jordan windows are often associated with this balance Series. The only other possibility would be the Series 351, which has a bottom shoe depth of 1"; the Series 390 has a 1-1/8" deep shoe. See the picture below to get an idea of what I'm talking about. If the shoe is more than 1" deep, then the Series 390 is the way to go. Let me know if you have any other questions about identifying this balance.

Comparison of the S351 and S390 balance shoes.

I believe you want the Series 390, based on what you've described. Odds are that your shoe was once 1-1/8" but wore down over time from friction. These parts are only plastic and such wear is normal. I think it's perfectly safe to round up.

It's very common for this kind of balance. These fittings are only plastic after all, so the constant friction usually shaves off 1/32" to 1/16" over the span of a decade or so. Not bad, considering, but you do have to mentally adjust your measurements when it's time to replace them.

Please feel free to reach out if you had any other questions!