To give you perspective on the bullshit you may be reading on the internet:
https://www.endocrine-abstracts.org/ea/0010/ea0010s2
2005 marks the 100th anniversary of the creation of the term hormone by Ernest Starling. Although its biological effects were known since antiquity, the name testosterone (T) was coined only in 1935, when Ernest Laqueur isolated it from bull testes. The road to this isolation was long: John Hunter had transplanted testes into capons in 1786 and Adolph Berthold postulated internal secretion from his testicular transplantation experiments in 1849. Following his observations, testicular preparations were used for therapy, popularised by self-experiments of Brown-Séquard (1889), which can at best have had placebo effects. Nevertheless, testis preparations were consumed until quite recently for the enhancement of virility. In the 1920s Sergio Voronoff transplanted testes from animals to men, but their effectiveness was disproven by the Royal Society of Medicine in 1927. Modern androgen therapy started when T was chemically synthesized independently in 1935 by Aldolf Butenandt and Leopold Ruzicka.
From the 1970s, the newly developed testosterone immunoassays made serial testosterone determinations in blood possible and, when applied to pharmacokinetic studies, it turned out that all available testosterone preparations resulted in unphysiologically high or low serum levels, which were undesirable in substitution therapy. Clinicians assembled at a workshop on androgen therapy sponsored by WHO, NIH and FDA in 1990 came to the conclusion: ‘The consensus view was that the major goal of therapy is to replace testosterone levels at as close to physiologic concentrations as is possible’88 and demanded that new testosterone preparations better suited for clinical use be manufactured.
Direct RIA for E2/TT measurement was developed in late 60s and available commercially by the early 1970s. There was no one accurately measuring serum TT/fT levels in the 30s if you are referring to the 1930s.
These threads should give you a good start. The reference range for TT has been 300-1200 ng/dl since the 1970s. Recent harmonization work by CDC to standardize TT assays by LC/MS-MS has moved that range at most to 300-1000 ng/dl.