27 3 HX CMC 7 or 27-4 AR5 CMC 1
Thank you for reaching out to us. We're happy to look into this. We would also like to see an image of the inside of the balance’s metal channel, where the innerspring connects to the pulley mechanism; this connection is located in the middle of the channel. If the balance is damaged, you'll have to use an undamaged version as a reference.
Was there a specific reason as to why you switched to the 27-4 stamp?
Thank you kindly for the additional photos and information. Based on your photos, I recommend the S380-28 or S385-28. The best match will depend on the depth of the bottom shoe, so you'll have to measure as shown below.
Your old stamp is calibrated for a sash weighing 13 to 19 pounds, so we would recommend the 2730 option if your sash weight falls within this weight range.
The 2740 stamp option is for a sash weighing 19 to 26 pounds, which would be too strong for the sash if it's 14 pounds.
Please let us know if you have any questions.
