<p>A commenter (below) tells me the green bit is the top-latch mechanism and that seat is an MB Mk GRU-5. Note these diagnostic points:
GRU-5: Face curtain strap routed around the headbox assembly-
GRU-5: No rocket motor initiator on the outside of the drogue gun (cylinder with red stickers)-
GRU-5: Shoulder Harness attached to the headbox assembly (clearly visible here)-
</p><p>This is the seat in the simulator, probably not fight qualified today... besides having no pyrotechnic stuff in it, any inspections it once passed must have long since expired...
It sure looks the part. I thought the green cylinder was a pyro delay, or rather, an empty stand-in. 
</p>
DSC_0095
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/9998127@N06">Bill Abbott</a>
<p><a rel="nofollow" class="external text" href="https://www.flickr.com/photos/wbaiv/6091233641/">Grumman A-6A Simulator Bombardier / Navigator (B/N)'s Martin Baker Mk GRU-5 ejection seat</a>
</p>
<ul><li>Uploaded by <a href="//commons.wikimedia.org/wiki/User:High_Contrast" title="User:High Contrast">High Contrast</a></li></ul>