In general, here are some things to look for in Carlton (and Raleigh Carlton, and probably all bikes 1950's-1970's). First, try to identify the decade. This can often be deduced from the type of lugs and fork crown, although I am not sure when Nervex Professional lugs were released, maybe 1960 or so, and if as you say that your bike has "lugs like a Raleigh International", then they are Nervex Professional. A bottom bracket oiler hole or pump pegs suggests a 1950's bike.
The serial number on the bottom bracket can often pinpoint the year, check the website http://www.carltoncycles.me.uk or http://www.retroraleighs.com (imho the latter has slightly more accurate serial numbers, especially for the 1960's and beyond.) A serial number (number only) stamped on a rear dropout indicates a mid-low end bike (531 db main tubes / forks at best, 531 plain gauge or carbon steel much more commonly.)
Look at the seat cluster. Wrapover stays are pre-1973. Conventional stays are post-73. Oversized seat caps on team pros and carlton pros 1974/5-onwards.
Look at the rear brake bridge. This is usually crap on a Carlton bike, but the very best bikes often had something that was nicely finished. In later years Carlton had 2 levels of 531-throughout bikes : the ones with crappy brake bridges (Raleigh or Carlton Competition), and the ones with good ones. The crappy one was a tube with 3 holes in the back and a washer / reinforcement brazed through the hole, and lumps. The good one (in later years) was a hayden with reinforced tangs and a waycool drilled barrel-shaped brake-mount - like on a TeamPro or CarltonPro.
If the vintage bike has forged dropouts or advanced braze-ons (e.g. for shift levers, or no fender eyelets => racing), it's almost certainly 531 db main tubes, or 531 throughout. For example, if your bike has braze-on shift levers, it's quite likely a carlton franco-suisse or franco-italia, a bike that combined "the best of all 3 countries - france/switzerland or france/italy and england". That bike had chromed lugs, i have 3 sets of pictures of that bike.
If the bike has stamped dropouts, look for signs that it's a high-end bike. This might include : rapid taper chainstays (no dimples), pencil stays (literally taper to pencil diameter), chater-lea (way oversized) bottom bracket, etc. I have a late 1940's early 1950's carlton flyer with all of these attributes.
Carlton in particular tended to CHROME EVERYTHING THAT MOVES. Atala did likewise. So, the existence of chrome on a Carlton is no surprise, and it often appeared even on very low-end bicycles, even carbon-steel bikes.
Another thing you can do is to weigh it and/or compare it to another bike of similar size. I can tell with my eyes shut when I pick up a Flyer or a Carlton Pro because if i'm not holding on tight it will fly up out of my hands and hit the ceiling, these bikes are way frigging light !!
- Don Gillies
San Diego, CA