I'll quote a snippet from user fluffyclouds on johnswentworth's original "Making Vaccine" post:

"There is another Covid-19 peptide vaccine developed by a Dr. Winfried Stöcker. He injected it into ≥64 volunteers, and the results he published look promising. They show both a good level of IgA, IgG and IgM antibodies and ≥ 94% neutralization for the vast majority of the test subjects. According to him (last paragraph of his blog post), none of the test subjects have reported any relevant adverse symptoms.

He describes the manufacturing in his blog (see translation below):

Man nehme dreimal 15 Mikrogramm rekombinante RBD der S1-Untereinheit (Arg319-Phe541) für eine Person. Als Adiuvans habe ich Alhydrogel von InvivoGen verwendet: Ordentlich durchschütteln und davon 200 Mikroliter mit der Tuberkulinspritze aufziehen. In eine größere Spritze 10 Milliliter Kochsalz aufziehen und die 200 Mikroliter dazugeben, mischen. Davon 500 Mikroliter pro Schuss, mit denen man seine Portion Antigen vermischt. Alles hübsch steril.

I've attempted a translation and added some of my own understanding in [square brackets]. Though I'm a German native speaker, I have zero domain knowledge in this field, so please correct me if anything is wrong:

Take three times 15 μg [three doses of 15 μg per person, spaced days apart - see result data linked above for timing] recombinant RBD in the S1 subunit (Arg319-Phe541) for one person. As an adjuvant I used Alhydrogel by InvivoGen: shake thoroughly and then draw 200 μl with a tuberculin syringe. Using a larger syringe, draw 10 ml saline solution and add the 200 μl [of adjuvant], then mix. Of this mix, use 500 μl per shot and mix it with the antigen [the 15 μg recombinant RBD]. Do all this in a sterile way.

If (!) these instructions are exhaustive, it might be easier, though possibly more expensive to produce than RaDVaC. Googling Arg319-Phe541 suggests that 100 μg (6 doses) / 1000 μg (66 doses) of this RBD can be bought for 310 € (52 € per dose) / 1130 € (18 € per dose), though there may be cheaper offers. I have no clue if the Arg319-Phe541 RBD I found here (230-01102-1000-RB listed on biocat.com and raybiotech.com) would be of the right kind to use in a vaccine. 

If you have the relevant domain knowledge to evaluate how complete these instructions are or what other risks and benefits compared to RaDVaC this vaccine may have, I'd really appreciate a comment. Likewise (and especially) if you know where to buy the kind of Arg319-Phe541 RBD used for this vaccine.

If you speak German or are comfortable with DeepL: the current edition (06/21) of the German magazine "Der Spiegel" has some more background on its development on pages 44 - 46: PDF (available for free due to misprints).

Edit 1: Detailed serological results (in English) were posted by Dr. Stöcker in May 2020 when he tested the vaccine on himself first."

I'm curious about this approach since there does seem to be better data supporting its efficacy than there is with RADVAC. A few questions for the biologists on LW:

1. Do websites selling omicron spike RBD like SARS-CoV-2 Spike RBD, His Tag (B.1.1.529/Omicron) (MALS verified) - ACROBiosystems typically require special licenses to purchase their products?
2. Most of the proteins sold by sites like the one above mention that they have a "His Tag". Some googling shows that this means some additional amino acids were added for more convenient purification and separation. Does it make sense to make a DIY vaccine using a protein that has a His Tag attached to it? Or would it have to be removed for safety/efficacy?
3. In the case of Stocker's vaccine, these proteins were injected. Is the provided purity from online stores sufficiently high to have a reasonable expectation of safety for injection?