The main improvement of the Bedrock design was in the frog, which holds the blade also known as an iron. An issue with the Bailey design was that the frog was secured to the upper side of the sole, and the iron extended unsupported through a slot machined in the sole of the plane. This combined with the thin blade often led to "blade chatter" because the blade was able to flex, causing an uneven surface. The Bedrock design has a frog which extends through a much larger slot milled in the sole of the plane, providing support to the iron almost to its cutting edge. This combined with a better mounting of the frog to the plane body provided a more solid bedding of the iron to the plane body, hence the name bedrock.
In addition to iron support, another problem with the Bailey design was that the frog mounting screws were under the iron, so the iron and the cap iron must be removed in order to adjust the position of the frog. This adjustment is necessary to vary the opening at the "mouth", which refers to the position of the iron in relation to the front of the slot in the sole, and which is used to control the size of shaving taken by the plane. The Bedrock design incorporated a new adjustment method, in which the entire frog could be wound forward or back, thus adjusting the mouth, without removing the blade.
A drawback of Bedrocks, shared with Baileys, is the thin iron, which were cheaper to produce and believed to be more easily sharpened. Indeed, on most Stanley irons the functional surface is laminated with hard, wear resistant steel in the first inch or so and mild steel in the remainder of the iron. Modern irons from other makers are much thicker and are 100 percent tool steel, hardened to about Rockwell 62.
Since the cheaper Baileys were kept in production along with the Bedrocks, to make the distinction easier, square designs were modelled in the body of the bedrock planes.
Long discontinued, Bedrocks are still sought after by both tool collectors and woodworkers. Some users prefer to fit thicker irons, which are available to suit most plane types but may require modifications to support the greater thickness behind the cap iron.
No #601 was ever produced by Stanley Works, but a "601" is indeed available from a custom plane maker. This "601" even has a lateral blade adjustment which the #1 never had.