Is that a big old tube regulated power supply under the receiver?
Pretty sure it's a Gates modulation monitor.
Believe a first ever was made last night also... Joe PJP and I were both using our NC-400s. Prolly the first time in many years, if ever, 2 stations were in QSO using that rare receiver.
A pair of NC-400s on the air at the same time....highly unlikely on a good day, unless it was that modified Leary beast that consisted of 2 NC-400s lashed together permanently with copius modifications. Might have a shot of it kicking around somewhere. I've listened to Joe's 400, audio reminds me a lot of the SP-600. A truly attractive receiver as well, sorta like a NC-183 on steroids.
Where would it fall on your 'bang for the buck' scale John, and more importantly - does it use Litz wire in the IFs?