Hard to tell from the photo, but to me the breather tube looks like to be already capped or taped up.

 As Malsal says, the mixture adjustment is opposite to what you would expect (and every other carb I've ever seen). These HIF (meaning horizontal(?), inner float) type carbs have the float bowl at the bottom and the adjustment screw works on a lever, which is why it is counter-intuitive. They can also be bl**dy difficult to adjust the mixture because the lever is bi-metallic and flexes a tiny bit as the engine warms the carb. When you try to adjust it with he car sitting still and the bonnet up, the lack of air flow allows hot air from the exhaust manifold to rise, heating the carb.
The other picture is of the lever removed from the carb. The one on the right is the bi-metallic devil. The one on the left is one the author of the photo modified to make it not flex with heat. The tiny slot at the tip is where the adjustment screw pushes against it.

In the pics I attached (not mine but collected from this forum) you will see the inverted carb wiht its bottom cover removed to show the float (yellow) the main fuel mixture jet (dirty white in the middle) and the lever on the right, held down by the screw with the spring. at the right of the picture you can see the fuel inlet nipple and the overflow nipple below it. The cast aluminum tube with the fin is the boss around the mixture adjustment screw. In the car, you approach it from the angle of the fuse box, roughly. Another challenge is getting a stubby screwdriver to engage the two slots in the head of the screw.

If the breather tube nipple is capped already, I'd advise not touching the mixture until you are more familiar with the car, and it with you.  If it is uncapped, and running OK, again do not mess with it unless and until you have to.

In the mean time, it might run better with the spark plug leads attached to the plugs!
Enjoy your new ride!

Also, welcome to the assylum!

As Dan said it looks like a HIF 44.
If you measure the throat it should be 44mm or 1 3/4".
When you cap off the breather tube you will need to alter the mixture to suit, the mixture screw screws out to lean it and in to richen it which is opposite of the HS series carbs.

Thanks for the identification Don, and thank you for the heads-up on the auto flame control.  Just acquired this car, and it's also my first SU carb.

It is a SU HIF type, most likely HIF44 (bore 44mm).

The brass nipple above the fuel inlet hose is the bowl overflow - unless you bring marshmallows, connect a tube (hose, metal tubing etc.) to it and lead the tube away from the engine and down to the bottom level of the car. If your float valve fails, fuel will be pumped out this tube, right above your nice hot exhaust manifold.

The other nipple beside it and closer to the engine is a vacuum connection. It should be either capped (plugged) or connected to the crankcase ventilation hoses - on an engine with a non-vented oil filler cap. I see your engine has a filter-type crankcase breather, so this nipple should be capped on your car. I'm not sure about vacuum assisted brakes, but they may also connect there.

Can anyone id this carb for me? Thank you in advance.