The breeder would have told you if he was of show quality (if the breeder was honest). Markings are the LEAST important element for either breeding or showing -- whether he is properly structured and moves well and a million other elements would be more important for showing, but he would likely be penalised for his markings even if he were perfect in other ways. He has very little mask and a lot of white -- generally you want red well broken up with white, eg a good mix of red and white, and a distinct mask and blaze.
Very few dogs are of breeding quality. First off, you need to be sure his parents are totally clear of murmurs at age 5. he would need to be a least 2.5 years old and also certified heart clear by a cardiologist (*not* a vet -- they are very poor at hearing the eearly murmurs you are checking for). Because about 50% of ALL cavaliers have amurmur by age 5, this eliminates half of all cavaliers from breeding from the start -- their parents will get murmurs by age 5, or they will have them. MVD and early onset murmurs is a leading cause of death in the breed and knocks several years of the breed's average lifespan so breeding for heart health is a top priority for anyone who cares about the breed.
Then: you need to test patellas, xray hips for hip dysplasia, have a vet eye specialist test eyes, and ideally, you should have your dog MRId for signs of the skull malformation that can lead to syringomyleia -- the malformation affects 90% of all cavaliers -- and also to check for whether his brain is protruding into his spine (a high number have this), or if there are syrinxes (about half+ have these). If your dog has any symptoms of SM before 2.5, and has any syrinxes on MRI, then it should not be bred.
The same needs to hold true for the dam.
So there are very serious health and conformation tests that a dog needs to pass before it would be considered of a quality to breed -- very very few cavaliers are of this quality, but unfortunately, many people just breed them haphazardly. One direct result of this type of indiscriminate breeding is that half will get heart murmurs at a young age and almost all our dogs will live several years less than another breed of similar size. Many will die a very slow and unpleasant death from complications around MVD.
That's why on this site, I have made health awareness a number one priority, and also, the need to support responsible breeding and responsible, health focused breeders. The breed is widely considered to be under serious pressure for its actual survival due to the health problems now bred into the breed.
None of us should risk contributing to any further decline but instead, support those expert breeders who are working to rescue the breed from this possible pending disaster.
Unfortunately Ireland has a particularly high number of 'backyard breeders' (people with little to no breeding experience who just breed any two cavaliers in order to make some money off of puppies) and puppy farmers who breed cavaliers in mass numbers then sell them overseas or in Buy&Sell (we are the puppy farm capital of Europe and lots of these poor quality cavaliers find their way into pet homes where they are, even more sadly, bred themselves, passing along those poor genes). Also sadly there has not been a strong health focus in the breed club, so a puppy buyer needs to be extra cautious.
The best way for anyone to find out if they have a show quality dog is to get involved with their local breed club and attend shows, and ask to have their dog evaluated by someone with expertise. Breeding should never be even considered unless it is known you have a dog with excellent genes and who has been throughly tested to show that there are genes worth conserving. Even then, expert advise and knowledge of pedigrees and genetics is needed to avoid the catastrophes of passing along devastating conditions like SM, curly coat/dry eye, episodic falling syndrome, painful hip dysplasia, and so on. Most of these conditions are not actually seen in a parent -- they are genetically hidden or will only show on testing -- thus only expert testing and knowing the pedigree well and the health history in the dog's line will help a breeder make correct choices in a mate.
You can see in the many of us who own cavaliers with some of these breed-specific conditions the heartbreak that happens when dogs are bred without testing or any awareness of health issues within the line.
