The Sansui 1000 is very different from the Sansui 1000a. Via this site it seems the relatively common 1000a was manufactured from '64 through '72 (!) and uses the formerly rare 7591 output which is now being manufactured by several vendors. The very rare 1000 apparently was manufactured in '63 only and uses the oddball 25E5 (PL36/CV10341) output with the distinctive anode on top.
The Sansui 1000 is to my eye much nicer looking than the 1000a and the 25E5 has the advantage of actually being relatively cheap for an NOS pentode. Here are some photos of a customer unit take at Austin Stereo:
Note the connectors to the tops of the outputs at the top of the second picture. Make sure you label them when removing the tubes. They need to go back to the correct tube! The build quality is top notch, as one can always expect from Sansui. You gotta love those transformers. The 1000 is a very nice sounding receiver with a fine tuner and enough power to drive full sized speakers.
For those interested, here is a close up of the 25E5/PL36/CV10341 output tube.