Can't find my exact balancer code
Thanks for posting. Channel Balances are not identified by codes; rather they are identified by the style of the nylon attachments at either end, as well as the length of the metal channel. It looks like you have either a Series 351 or Series 390 Channel Balance. The only difference between these two Series is the 'depth' of the bottom nylon shoe. With the Series 380 the depth of this nylon shoe is 1", whereas with the Series 385 it is 1-3/32". Compare with your own and see what is best.
Once you know which balance Series you have, you must choose the proper length of your balance. Measure the length of the metal channel, not including the nylon attachments, to obtain this length. Your balance is likely 28" long, meaning you have either a S351-28 or S390-28, but it is best to confirm this to be safe.
inally, you will need to choose a stamp option. Your stamp code of 27 4 conforms to our stamp option of 2740, for a window sash in the weight range of 19 through 26 lbs. Let us know if you have any questions.