Usually fuse size is stamped on its end cap, always replace with same size for proper protection.
@imhififan -- Right, I’m aware of how to see a fuse rating from the markings however, there was a fuse in there of questionable lineage so was seeking the RIGHT value.
@vair68robert -- Thank you. Fortunately for me Msr. du Pech of Jadis e-mailed me just this morning with the answer:
8A slow blow 6.3x32mm for the mains
160mA slow blow 2x20 for the cathode
Thank you all for your response!