The Gillette Tech was produced by Gillette from 1939-1979. There are a few different designs available ranging from a ball end thin handled model, a flat end thick handled model, to a travel size short handled model. In classic fashion, this is a three piece razor with zero moving parts.
Pro Great for a mild shave but also great for advanced users
The design of the head is slanted in a way that allows for a mild shave that should not cut ones skin. Another plus is that the head is quite small due to the three piece design, meaning it is easy to get under the chin as well as under the nose. This is great for those new to using a double edge razor as it will feel familiar in size while not being too aggressive.
For those looking for a more aggressive shave, there are blades out there that are aggressive themselves and when paired with this mild razor, it makes for a good combo.
Pro Very durable
One of the reasons this razor is so easy to find, is that it was built very well. Ranging from the pre-war models all the way to the ones manufactured in the 1970's. It could be very likely your father or grandfather has one laying around (thanks to its popularity when manufactured), as they do not tend to break. At worst, the plating may be scratched or wearing off, but even then the razor still functions as intended.
Pro Simple to take apart
The three piece design makes for an easy to understand razor when taking apart to remove old blades and add a new one. Simply unscrew the top from the handle, separate the two top pieces and then gingerly grip the ends of the blade to remove from whatever side it is stuck to (usually due to the wax on the blade left over from its wrapping paper), then drop a new blade on the top piece with the screw, reassemble.
Pro Very easy to find for cheap
One of Gillettes most popular double edge razors, while not produced anymore, is quite easy to find on eBay and other resale marketplaces, even thrift stores or flea markets. On top of this, due to how many are out there still, they can be had for under $10 (though the gold plated ones may cost a bit more).
Con Difficult to find brand new and unused
While there are some places that offer refurbished models, for the most part it will be pretty difficult to find one that is in brand new condition. While some can still be found sealed (due to the vast quantity Gillette manufactured), they will cost quite a bit more and will need to be hunted down. This may require too much money or time for the average person who wants a new razor.
Con Totally non adjustable
There is nothing to adjust with this razor, meaning you can not change the angle of the blade short of changing your grip angle. So good form is key here, though not always necessary due to being a mild shave to begin with. Someone starting out with DE (double edge) razors may want something that has more features, such as adjustable blade angles or quick blade removal.
Con Blade removal may be intimidating
Some DE razors out there offer quick and easy removal and insertion of their blades. While a three piece razor isn't all that complicated, it may be intimidating to a new user or someone used to even easier methods. Being conscious of where you grip the blade when removing and replacing is key, as if the sides are gripped over grabbing from the ends, you will quickly notice you just sliced your thumb and finger.