Seeking Channel Balance

Thanks for posting. I'm afraid I'm going to need more information to be able to help. 

First, could you provide a picture of the balance, removed from the window? Specifically, could you show pictures of any attachments at either end of the metal channel? 

Next, could you also tell us the length of the metal channel, but not including the end attachments? 

Finally, could you confirm the stamp says '21 12'? If so, could you weigh your window sash? That precise weight is critical in making sure you select the right stamp option. Thank you!