[Milsurplus] 3ASP1 vs 3XP1 CRT

[Skywarrior]

Hi All,
I did not see my last post on this so I will try again.  I have an old CEI receiver that incorporates the 3XP1 CRT.  It is a 1 X 3" CRT, it seems identical to the 3ASP1 (which later CEI receivers/SDU's utilized) but since the designation is different and I vaguely know the designation also indicates characteristics I am not so sure I can just plug in one of my spare 3ASP1 CRT's.  Hence my question, can one be substituted for the other?  If not, does anyone know of a source for the 3XP1??

TIA
Bruce