10 Days with the Seiko MM300

If you follow me on Instagram (@vintagediver), you’ll probably have seen that I recently took a vacation to Puerto Rico (yes, it was freaking awesome). You may also have noticed that I’m a “vintage guy” when it comes to watches. Normally I tend to wear a different vintage watch each day, although I have been know to wear the same watch for a few days in a row (crazy, I know), especially if it’s my ’79 Tudor blue snowflake.


Now, I know lots of you guys will pack several watches for a trip but I don’t like the idea of traveling with a bunch of my watches, having to worry about taking them on a plane or leaving them in the hotel. So, I will usually pick one watch for my trip and just have to suffer through the withdrawals. Since this vacation was to a hot and humid tropical locale and I knew I’d be spending lots of quality time in the pool and ocean, I chose to go with a modern watch with a screw-down crown: The Seiko SBDX001 Marine Master 300m, or MM300 as it’s commonly known. The MM300 comes on a great bracelet, but I chose to wear it on an Isofrane strap for comfort in the muggy weather, plus it just looks killer on that strap.


As a result of my choice I ended up wearing the same watch, a modern watch, for TEN DAYS STRAIGHT! Amazingly the world did not end, nor did I implode! Actually, I was very happy with my choice and really became quite attached to the MM300.  I’ve always loved this watch, and it has fast become my favorite modern watch. Of course, it’s a modern ‘heritage’ version of the vintage 1960’s Seiko 6159-7000/1, which is a timeless classic and one of my all time favorite vintage watches. It’s at the top of my ‘must have’ list, but sadly still eludes me.


The MM300 is big but not huge, measuring 44mm wide (42mm across the bezel). It is a bit on the thick side at 14.6mm, and as such it does sit kind of high on the wrist. I’ll admit this was a small concern for traveling as I didn’t really want to bang it on stuff on the plane and such (yes, I’m that kind of collector). That said, the MM300 really wears well on the wrist, and its height wasn’t an issue at all.  Never banged it on anything, and didn’t end up with any scratches or dings (whew!). The size and weight are very comfortable, especially on the Isofrane, which is quite simply the best and most comfortable rubber strap on the market, bar none.

The MM300 is also quite versatile, going from the pool or beach to a nice dinner at a fancy restaurant with ease. Now, it’s no Patek Calatrava, but it is nice enough looking and not too “toolish” to wear out for a nice dinner. Not sure how well it would fit under a cuff with a sport coat, but I don’t wear sport coats unless I absolutely HAVE to. And since Puerto Rico in September is hotter than Hell on a bad day, I definitely did not pack my sport coat.


I wore the MM300 every day, from the moment I got up to the moment I went to bed. I wore it bike riding, hiking, in the pool, at the beach, and yes, even in the shower (the horror!). It easily handled the transition from 90 degree temperature and 90% humidity to the cool air conditioned hotel room and back outside several times a day with no ill effects.  As could be expected from a professional divers watch, it performed admirably under all these extreme conditions (that’s sarcasm boys and girls).

Once I landed in the Eastern Time Zone and had set it, I didn’t unscrew the crown once. With a 50 hour power reserve,  the watch stayed wound and sealed and ran the whole time as it should, keeping near perfect time. As a guy who lives on the central coast of California where the weather doesn’t vary much, it was definitely a departure for me to have the high heat and humidity.


Normally I really enjoy the variety and novelty of wearing a different vintage watch each day. I wear them carefully, taking care not to get them wet or whack them on the door handle. However, I have to admit it was kind of nice just strapping on the MM300 in the morning and not worrying about it from that point on. Sure I’m cautious to not smack into something, but that’s become an ingrained habit (like most of you I’m sure). Other than that I only really thought about it when looking to tell the time, or when I was shooting a picture of it (yep, did lots of that….watch nerd!) in the various exotic locales.

So, what did I learn over my ten days with the MM300? Quite a bit to be honest. I learned that first and foremost I LOVE this watch. It’s everything I want in a modern watch. It’s comfortable, reliable, robust, versatile and stylish. Everything a WIS could need on a vacation, or at home for that matter. Plus it’s pretty damn photogenic, which comes in handy when you’re an Instagram addict. It is built like a tank, but beautiful enough to wear anywhere. The combination of that sweet glossy bezel and the chunky steel case with its brushed and polished surfaces is truly a work of art. While I did miss all my vintage lovelies, the MM300 made it tolerable. I also learned that I can indeed wear a modern watch for an extended period of time and I will live to tell the tale…

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Christoph (Instagram’s @vintagediver) is a long time collector and lover of all things vintage, starting with comic books when he was a kid (he still collects them). His passion for watches began in 1997 when he was gifted a family heirloom vintage Omega Genève by his step-father. That started him on the watch collecting path—buying and selling vintage watches of all sorts, with a special appreciation for vintage dive watches and Seiko.