Hi Stu
Yes, HIRST it is.  

 Here is a better pic....
The lock on this gun is in heavily worn condition.  I'll get it cleaned and reasonably repaired to working order.  I'll re-post so that you can see how worn this lock is.  Considering this, it's amazing the rest of the gun is in as good a shape as it is.  This gun's seen a lot of campaigns.  
Rick