Most the building not very dirty. However the part you showed the close up of is going to take something a little stronger to get rid of the paint or whatever that it. Talk to Eaco chem on their One Restore and Prosoco has a newer product called Reveal that might work since you have all those windows to be concerned about - https://prosoco.com/product/reveal/
I and a few others had a long thread on here about a year ago on restoring older historic buildings and I put a ton of info in there if you can find it along with some links to approved GSA methods.
A lot of the cleaners for these type building have sodium hydroxide in them and then they want you to buy their neutralizer, which you’ll need, but it’s generally just oxalic or acetic based which you can do your own.
I found the thread - Orange appearance of Lueders Limestone - #22 by John_Martinez
suggest you read it. Good luck. Do not be cheap on your bid. That’s probably a $5,000 job at least for just that front facade if they want it done right. You’re going to have a traffic management problem on this one(pedestrian). Going to need helpers for that, etc. I did another thread on all of that somewhere.
