GIA Certified

We exclusively propose diamonds certified by the GIA, the one and only grading authority for the diamond trade worldwide. Other laboratories over-grade stones, giving you a false sense of quality and value.

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100% Custom

The perfect engagement ring does not already exist in a display. It should be custom made with you, for you. Our onsite expert craftsmen will make that dream a reality.

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Friendly Support

At our studio, you will be treated in a private setting with all the focus on the making of your diamond purchase experience the most personal, relaxing, and educational diamond buying experience.

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Personalized Service

Our best engagement rings are created with a personalized service. The service begins with a consultation with Sevan, who will learn more about you and your inspiration, helping you to develop your ideas and final vision.

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A Brief History…

Design by Sevan - Custom Diamond JewellerySevan Tosun was born in 1977 in Istanbul, Turkey, the former capitol of the Byzantine and Ottoman Empires and home to a tradition of fine jewelry spanning over two millennia. At the age of 10, Sevan carried on his father’s legacy and began a full-time apprenticeship with one of the finest jewelry houses in Istanbul. By age 16, he had learned every facet of the trade, cultivating the highest level of skills a jeweler could achieve in metal, diamond setting and design, imagining intricate designs and creating pieces from start to finish.

With an amazing array of skills and dreams of a better life, Sevan left his roots in Istanbul as a teenager and headed for Canada with just $250 in his pocket. Connecting with a relative who had already emigrated to the Canada Sevan arrived in Toronto industry. Within a few years, Sevan developed a reputation as the finest jeweler in the area, and in 2000, he founded A.S.T.Jewelry ,Today, Design by Sevan A.S.T Jewellery stands as one of the premier Engagement Ring boutiques in Fashion district Toronto.

Jewellery Design Awards


  • Sevan is…for lack of a better term…the man! My fiance has had her engagement ring for over a year and loves it just as much today as the day I proposed and she still gets compliments on it from random strangers. As a guy, buying an engagement ring can be a pretty intimidating and a slightly terrifying experience. Sevan is calm, honest and to the point. I shopped around quite a bit and found Sevan to be the best on price and on style. I tried big stores like Birks who offers you Perrier when you come in the front door (guess what – you pay for that whether you think so or not) and smaller independent places on Queen west (which was definitely more expensive and I wouldn’t even have been given the opportunity to choose the diamond myself!). Beyond the far better prices and quality design, the best part of my experience with Sevan is that he actually seems to have your interests in mind. We stayed within my budget and he helped me pick a great diamond. Normally most jewelers just go by the four Cs…but Sevan taught me about things like the size of the diamonds table. Which meant that he ended up suggesting a diamond which had a smaller carat size but looked larger to the naked eye because of the table size. He also emphasized the proportions of the ring which can influence how much it sparkles…or the ‘fire’ rating of the diamond. All this to say we are incredibly happy with Sevan and his work and will be going back for our wedding bands..

    Stirling Lafrance
  • I found Sevan through a referral and he most certainly has lived up to the reputation that precedes him. Sevan helped in all aspects of conceptualising; sourcing and building the most amazing custom engagement ring. His office is conveniently located in downtown Toronto. I travelled from Ottawa to meet Sevan and found it very easy to get from Toronto Island Airport to his office in minutes. Sevan and his office are both welcoming and put you at ease as you venture down the path of making a very large purchase. He instils confidence and trust when you meet him; which will allow you to move beyond validating your jeweller and on to the fun part; designing a dream engagement ring. He spends time ensuring he understands the concepts and then lays out your options out front to ensure price and expectations are in line. We spent a few weeks looking for the perfect cushion cut diamond that blew me away. After the diamond was sourced and purchased we quickly moved to make the ring. Sevan met and made every timeline I asked of him. The communication during the process was excellent and I rarely waited minutes for a response from him. I highly recommend Sevan for his professionalism, customer service and ability to deliver on the most amazing custom engagement ring and would be willing to act as a personal reference for his work and character

    Seamas Egan Ottawa, Ontario Canada
  • Sevan was absolutely amazing to deal with. He found the perfect diamond and complemented it with an incredible design. I live in Ottawa and his store is in Toronto, and I never even needed to make the trip. We exchanged emails, designs, and phone calls in order to complete my request and my ring is even more beautiful than I could have imagined. I would absolutely recommend him to anybody and everybody I know. Thank you Sevan for my perfect dream ring..

    Vanessa Sanschagrin
  • We had an amazing experience with Sevan! We had to have our wedding rings designed on short notice and Sevan delivered on time and the rings turned out absolutely beautiful. The experience at his studio is pleasant and he is very patient. He provides a lot of valuable information with regards to style, and type of metals that would be optimal for certain designs. Sevan’s experience shows. He is a true professional and knows his art form in out. We would recommend Design by Sevan to anyone looking to get a truly personalized engagement ring. Thank you Sevan.

    Anna Gondzik
  • Buying a ring from AST was a fantastic experience!! Can’t say enough nice things about Sevan. He runs an honest, pressure free business and has become my go to guy for all my jewelry needs.

    If you’re looking for a diamond ring for that special someone Sevan will make you the ring of your dreams for a fraction of the cost of the big guys… and treat you with respect along the way.

    Could not be happier!! Highly recommended!!

    Dan Pifs
  • My girlfriend and I (now fiancée) were referred to Sevan at AST Jewellery by a friend of ours.

    Taking a look at his site we found something we wanted (she wanted a coloured stone and we landed on sapphire) to which we promptly set up a time to go meet him and try it on!

    Not only was he quick to respond but he made us feel very comfortable with our flurry of questions and took the time to explain various cuts, clarity, etc. This man knows his craft very well and we could tell how passionate he is about it.

    We figured out what we wanted and moved forward. Sevan takes you along every step of the way, is honest, assuring, kind and simply a genuinely nice person. When making a big purchase and a big decision like getting engaged it just amplifies the excitement when the person you’re buying the ring from is so fantastic.

    A brilliant experience. Highly recommended and we’ll be back for the wedding bands and be referring any of our friends to him.

    Thanks Sevan!

    Justin Cumby

For many jewellers, making jewellery is a profession – for Sevan, it is an identity.

If an engagement ring design has caught your attention, make an enquiry with us today.

Specializing in Custom Diamond Engagement Rings

NO SALES PRESSURE SHOWROOM – No unwanted sales pressure. We promise!

  • Our trained consultants are NOT on commission. That’s what separates us from other jewellers. Feel free to come in and browse our store at your own pace. When you’re ready, we will be happy to answer any question you have.
  • Our personalized service focuses specifically on the customer. Visit our store and you’ll see we are truly on your side.
  • There’s no jewellery store better equipped to meet all of your engagement ring shopping needs.
engagement ring marriage proposal

We specialize in designing custom jewellery. If you’ve got an idea for a ring or another piece of jewellery, we can help bring your idea to life and offer advice on the design and details to meet your individual needs.

We design all our jewellery in-house and all commissioned rings are individually made for each client, this making us uniquely suited to offer customers great custom jewellery at affordable prices.

Questions? Ask us anything.