With lots of money and/or time. 1) Testing of the lumber. 2) Getting a grading expert to access the lumber, who's report you would be willing to except. 3) Calculating the required Fb would be and seeing which species and grades would work and using the minimum of what would be available in that area at that time. 4) Making an engineering guess based on what was normally used for lumber at that time and seeing if the calculations work.
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.