If you are buying someone's safe queen, and it is second hand, check the trigger pull. TNW pioneered the marketing of a semi-34 made with real German parts, and to their credit they spent a ton and made some quality semi-parts for their conversions. However early their first generation FCG had a pretty hefty trigger pull, after some time (maybe a few years into production--it has been a while and my memory is foggy) they altered the design to have a slightly lighter trigger pull. Still pretty stiff, but hey thanks to them you can shoot an iconic and beautiful weapon for 1/10th what a full auto NFA registered one would cost.
Also if it is second hand, make sure you know who built it. TNW was VERY kind to sell their grip conversion parts for many years to builders (it was only like $150 for the kit), they also sold receivers, and some "seconds" receivers were rumored to be offered for a group buy on Weaponeer back in the day-not sure of they ever made it into circulation. Therefore know your seller, know what you are buying.
If it is brand new, then obviously the aforementioned is moot, and go for it
“… corporations have been enthroned, and an era of corruption in high places will follow, … until all wealth is aggregated in a few hands and the Republic is destroyed.”
- Abraham Lincoln (Republican), Nov. 21, 1864