It appears you have either a Series 380 or Series 385 channel balance.
The difference between the Series 380 and Series 385 balances lies in the shoe.
Comparison of the S378, S380 and S385 balance shoes.
The series 385 balance has the 15-004 shoe which is slightly larger from front to back, as illustrated.
If you measure your shoe as it is pictured here, you should be able to determine which one you need.
Please let me know if you have other questions.
