Searching for 33 4 bsi oa

Hi there!

I'm afraid we can't identify your balance from this photo alone. We would need you to remove an undamaged balance assembly with the end fittings intact to compare to our inventory. 

Thank you for the additional photos! Based on what I see here, my recommendation would be the S380-34 or S385-34 channel balance. The crucial difference between these two parts is the depth of the bottom shoe so you'll need to measure as shown below to determine the best match. You will also need to select the 3340 spring strength option for your replacements. 

Comparison of the S378, S380 and S385 balance shoes.