Our favorite Black Mesa Science Team had gone through many iterations until the looked like we see them today, going from frightened, nervous wrecks to the somewhat goofy looking they are today. Let's explore how they changed over the years.
Version 1: Concept Art
The earliest version of the scientist, made by Chuck Jones. He has clothing different from any of the models, resembling more of a sci-fi suit than a lab coat. This version has round pitch-black glasses, which survived in the next version.
Version 2: Pre 0.52 Alpha
The second version of the scientist, found in a magazine which had Half-Life preview images, which bares familiarity to the one found in the 0.52 Alpha, the only differences being the stance and the head model, this version of the scientist is hunched over and its head model (known by fans as the Mad Scientist) has black glasses and a scar across his forehead
Version 3: 0.52 Alpha
These models are found the files for the release Half-Life 0.52 Alpha and unlike Version 3, are dirtier and have more scarring, mostly on the back of their heads. "Walter's" glasses look similar to the final scientist model, "Einstein" and "Egon's" heads are not the same color as the rest of the body and despite what it may seem, these models have no moving mouth.
Version 3.5: cine-scientist.mdl
This model is a mashup of Version 2 and Version 3, having the "Mad Scientist" head and the body of the 0.52 models. This model is only used once in the
techdemo.bsp map, where it is seen arguing with a Security Guard, only to be eaten by a Panthereye.
Version 4: Post-Alpha
This version of the model looked very similar to the previous version, but with less blood on the textures, but its stance and shape are still close to the 0.52 Version. The scientist's lab coat & slacks are both a clean, uniform white colour with a blue shirt underneath compared to the dirtier white coat & navy blue slacks seen in the previous versions. Something to note is that the Egon head was retextured into an early version of the Luther head.
Version 5: Raising The Bar
This version of the scientist appeared in the Raising the Bar book. It appears to have been rendered by Chuck Jones, or at least in a style mimicking his. The whole body has been overhauled with the final body model, high-resolution textures, black gloves, a red & black striped tie, and the glasses are transparent, revealing small eyes. Apparently, Deathmatch Highpoly Submodel for the Scientist is the late, pre-release revision of this version. The head and the body sheet textures are from the pre-release era. Interestingly enough, later version (seen standing behind early Luther on the Black Mesa Advertisement texture) of the RTB Glasses Scientist already has solid, non-transparent glasses. However, the only Scientist that was never seen with the gloves is Slick, meaning that his submodel and textures were still incomplete at the time.