kitsykeel

No necessarily. Here are some ways to tell the difference between 15-88 and 15-96:

15-88 has round stitch length control plate.
15-88 Bobbin case latch opens on the right. The finger is at 11 o'clock position (part #125291.)
15-88 Feed dogs drop.

15-96 has rectangular stitch length control plate.
15-96 Bobbin case latch opens on the left. The finger is at the 1 o'clock position (part #15277.)
15-96 Feed dogs do not drop.

Bobbins for both are the same #2518.

Both the 15-88 and the 15-96 have flat side of needle facing left and they thread right to left.

You can also go to The Needlebar website: They have a page for Singer Model 15 comparisons. This should help you identify your machine. Good luck to you. I am ready to order some items for mine tonight from Sew-classics.com (Jenny) and can't wait to start sewing on her.