Although we hear about amazing advances in high technology every day, it’s often the really low-tech ones that most cause us to say “Why didn’t I think of that?”. A case in point is the MP4000 Personal Post Office portable scale – a product that's been around in its current incarnation since the 70s, but that we still thought was worth a mention. Designed primarily for weighing letters in order to determine postage, the non-digital, non-electronic, and barely even mechanical little gizmo is nonetheless accurate enough that its use has been approved by the US Postal Service.

First of all, if you think the little scale looks charmingly retro, that could be because it's based on a design that dates back approximately one hundred years. Pocket scales that utilized a similar principle were in use as long ago as 1600.

To operate the MP4000, users hold it by a top-mounted ring, and attach their letter or other payload to an alligator clip on one side. This causes the scale to tip to that side. A loosely-mounted indicator needle hangs on the other side of the device, and will always point straight down due to the force of gravity. To obtain the weight of their item, users simply see which of the engraved numerical values that needle lines up with, once the scale has tipped.

Figures are listed in imperial on one side, and metric on the other, and go up to 4 ounces/100 grams. The heftier MP8000 Postagemiser model goes up to 8 ounces, or 200 grams.

Besides its role as a letter-weigher, the MP4000 has reportedly also found use in fields such as home brewing, field biology, cooking, and police work. It’s available online for US$4.75 plus shipping, which includes a current U.S. and international postage rate card. The MP8000 costs $10.95.