Medium-high tension spring used on pinball machine ball shooter assemblies. 0.035" wire diameter.
It's a good idea to replace the outer barrel shaped spring (No.10-149) at the same time as this one.
Reference:
10-148-4
Capcom SG-00107-04
Data East / Sega/ Stern 266-5001-04 green
Jersey Jack Pinball (JJP): 13-007007-06