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Any decent independent watchmaker should be able to service this for you if you don't need parts. There may be wide variations in price estimates depending on who you take it to - $250 - $350 Canadian is the range I would expect to pay. Some may not take it because sourcing parts is not always straight forward for these old Zeniths. I am in Toronto and I had one that needed a hair spring and a balance staff, so my watch guy gave it back to me. I bought a used movement on ebay and then he was able to fix it. Yours is a nice watch and the style looks to be early 60's but that is just a guess. Even the band suits it and is kind of funky. Zenith is a very under appreciated brand.
Hi @MTL514, and welcome to OF from a fellow Cdn. Nice piece to remember your father by; I agree with the others, get it serviced and wear with pride.
I am not a watchmaker (a physician, actually), but we do have several who are members here. As per a previous post, @Archer is a knowledgeable and highly respected watchmaker in the Southern Ontario region who may be able to help you out. I also know that there are a few independent watchmakers in Montreal. Based on web feedback (not my own experience) watchtyme at 137 Rue Saint-Ferdinand Suite 156 (http://watchtyme.net/) or OTA at 6865 Sherbrooke W (http://www.otawatchmakerandjewellery.com/).