Shoutout @stephen sawall for this.
This is all the versions I have found so far of the Vintage 30....
T3896 8 ohm Original Marshall Labeled
T3897 16 ohm Marshall labeled
T3903 8 ohm Celestion Labeled
T3904 16 ohm Celestion Labeled
T4335 8 ohm Mesa Labeled
T4416 16 ohm Mesa Labeled
T5321 16 ohm Marshall Mode Four
T5794A G12-60 S.E. 8 ohm
Special Edition
T5489 16 ohm
Relic 30
T5401B Vintage 30 8 ohm
Bad Cat version
T5731B G12- Vintage 30 16 ohm
Dave Mustaine V30
T5225 16 ohm 1777 cone
Hughes and Kettner
T5273 8 ohm 1777 cone
Hughes and Kettner
T3904A Vintage 30 16 ohm
25th Anniversary
These are all slightly different sounding Vintage 30.
"When you change the impedance rating of the speaker, you also change the inductance of the coil which changes the resonant frequency among other things. So if you have 2 identical amps and 2 identical cabs - one cab loaded with 8 ohm speakers and amp set to 8 next to one loaded with 16 ohm speakers and amp set to 16, they will sound noticeably different. The 16 ohm rig will usually sound brighter and deeper."
T3896 G12V 8 Ohm Vintage 30, Marshall label, 70w, 444 cone
T3897 G12V 16 Ohm Vintage 30, Marshall label, 70w, 444 cone
T3903 Vintage 30 8 Ohm cone stamp – 444 (standard specification)
T3904 Vintage 30 15 Ohm cone stamp – 444 (standard specification)
T4335 Vintage 30 8 Ohm cone stamp – 444 – Old original spec – now Mesa OEM
T4416 Vintage 30 16 Ohm cone stamp – 444 – Old original spec – now Mesa OEM
T5321 G12 Vintage MF 16 Ohm Custom designed for use in Marshall MF series cabs. G12-CV60.
"What I was referring to was the construction of the speaker itself. Taking a 16 ohm vintage 30 for example, if you simply decrease the speaker voice coil turns to make it an 8 ohm speaker, the chances that it would sound the same in all other respects are slim. By playing with other factors such as wire gauge and doping, they can me made to sound similar, but not identical.
So, it's important to know that when you are comparing cabs. Comparing two identical cabs operated by identical amplifiers, but one cab loaded with 8 ohm V30s and the amp set to 8 ohms vs one cab loaded with 16 ohm V30s and the amp set to 16 ohms, you are going to hear a pronounced difference in sound and performance. The differences will be partly the difference in electrical characteristics of the speakers and partly the resulting change in reactance of the amplifier.
Even so, I think you'll find that two 8 ohm speakers wired in series for a 16 ohm load will produce a deeper wider sound."
Both quotes are Steven Fryette.