I've been on the lookout for one of the first batch of Rex Ambassadors.
From images online I saw that they had squared off lather holes, however once I received this one I saw that there are a few more differences. I'll do another post here showing and listing them.

My normal modus-operandi is to change the razor and keep the other items constant, then change the "other items" and reverse the order of the razors. If possible, I keep the settings the same on all the razors for the first runsand once the first runs are done, I reverse the order of the razors and then try and get the best shave for the last runs, which normally means that I dial them to the max.
I decided that I would go from the oldest Rex (M3 Serial number) to the newest one (R4 Serial number).

For the first three shaves I decided to go with Master Soap Creations - Vintage Lapidus soap and splash, a Rubberset 400 with a G5 Synthetic knot and a Feather blade. The soap was chosen because of it's slickness and the brush was chosen simply because it what was up in my brush rotation. I was a spur of the moment decision to use a Feather blade.

Day one: 09 June 2025 - Rex Ambassador M Serial number.
The new Feather blade inserted, I dialed the Rex to 3,5. This pretty much gave me close to a 2-Pass BBS shave and the R-L/L-R strokes were really not needed. Not unusual but I did miss a small patch along my jawline.
I caught a small weeper which had closed by the time that I finished the shave.

Day two: 10 June 2025 - Rex Ambassador N Serial number.
This is the one that I've used the most and I know it to be a little draggy. As with the previous shave, this was also dialed to 3,5. Credit to the MSC soap I felt very little drag and as I expected and the first two series of strokes didn't quite get me to a BBS, however after the R-L/L-R pass I was BBS smooth. This time I didn't miss any spots.

Day three: 11 June 2025 - Rex Ambassador R Serial number.
As with the previous two, I again used a setting of 3,5. This felt a little less aggressive than the other two and again it took the three passes to get me BBS smooth.

So after the first three shaves:
Halfway through the shave-off and I get the idea that they have gently tamed the Ambassador down.
They all got me BBS smooth, but as I went through the shaves each one needed more strokes to get there.
I've found that blades generally don't perform well on their first and sometimes second shaves, so just observations and no conclusions.....

Now onto the next series of shaves.
 
 

For this round, I changed to Tabac soap and Eau De Cologne and the lathering was done by my Omega Boar. The rest of the gear stayed the same.

12 June 2025 - Rex Ambassador R Serial number.
I dialed the razor "fully open" which is just over the 6 setting. (This one very slightly overclocks by about a ½ setting.) The Tabac isn't as slick as the Master Soap Creations and a little drag showed up. On the first pass, I picked up a decent weeper and between the first two passes the only stubble left was the awkward spots. The third pass cleared the rest. After the three passes, this was the best shave so far as I expected it would be, although I was a bit sensitive on the left and right side of my neck area.

13 June 2025 - Rex Ambassador N Serial number.
The drag that I've always felt with this razor was back which obviously indicates that soap plays a big part in this. That said, I decreased the pressure and used all three passes to get me smooth.
The sensitiveness that I felt with the previous shave didn't show up later. This took over as the best shave so far.

14 June 2025 - Rex Ambassador M Serial number.
With this been the most aggressive and after the first series of shaves, I expected this to be the best shaver. With it dialed to the max, it was pretty easy to get a smooth shave. As with the "R" version there was a bit of sensitiveness in the left and right side of my neck a few hours into the day.
This version has less drag then the othet two even though the TopCap isn't as well finished.

What conclusions can I draw.
The first thing is that the first (M) version is the closest to a Gibbs.
The most efficient shaver: This actually surprised me! I found that the one with the N serial number gave me the best all round shave even though it is "draggy" and I had to use three passes to get there.
Which is the smoothest or most refined shaver: I would give it to the "M" version with the "R" a very close second

Were I forced to choose one... No we are definitely not going there!!!