SINGER MODEL? NEED BOBBIN HOOK

[Joe711]

Can anyone tell me which model of Singer this is?  Based on serial number it shows to be a Series 31 but I've bought numerous bobbin hooks for a 31-15 and they are slightly too large and are binding when turning the hand wheel.  Also recently bought a Series 15 and it fit too large as well....almost EXACTLY like the "31-15"'s I orderd.  Maybe I was sent the wrong parts originally...not sure...... Any help would be appreciated.  TIA

[Northmount]

5 hours ago, Joe711 said:

Can anyone tell me which model of Singer this is? 

Moved to leather sewing machines.