While it looks very nice, the NMUSAF P-61 is a postwar C model, painted as a wartime B (the C is distinguished by turbosuperchargers and broad-chord props, as well as other differences.) I'm not sure when she was last painted, but it was before I first visited the museum in 1978. A few years ago the museum added an upper turret (not sure if the C ever had one.) If you want to get really picky, she has an inaccurate rear blister (much too blunt) and a lot of the interior components are missing. But she's one of the few surviving Widows, so I'm not complaining.

The Black Widow at the NASM Udvar-Hazy center is also a P-61C, and carries the remnants of several paint schemes, including markings from when she was used by NACA for research purposes.
The only surviving wartime models of the P-61Bs are the one rotting away on outdoor display in China, and the example being restored at the Mid Atlantic Air Museum. I don't think any P-61As have survived.
SN