Cyma M1A1

[JamesAirsofterAgent]

Electric Cyma M1A1, used a lot but loved. Would come with battery & box. 

https://www.patrolbase.co.uk/cyma-cm-033-thompson-m1a1-military

[Tackle]

As has been pointed out, general rule of thumb is 60-70% of the current cheapest rrp, obviously signs of wear or damage can push that value down, or accessories that are worth having, such as mags & good quality batteries, can raise it.

Decent pics can help with an appraisal too.