I have not had one of these on my bench is a while. It has a .0033 suspension, seems to me it take a .004 or 0045? Nice condition the customer just wants it running and keeping time. How do you like my Goodwill Turn Table, its slick!
What's the serial number? That will help with the dating. I agree that 0.004 is the more typical size. What is the weight of the pendulum? Mine run in the 13-14 oz range. I notice that your pendulum is higher above the base than most. Being higher, it will run fast but then a thinner spring would help compensate for that.
That makes it late 1904. I have several Beckers that are slightly before or after that date. The pendulums are essentially 14 oz plus or minus a few. 18 oz seems quite heavy which probably explains why the spring is so different. But I guess if it runs, it's good to go!!
I don't think all are screwed in. Some I believe are just pressed in...chamfered end into a conical shaped hole. To date, I've never tried to even take one out...I did break one out of the anchor...a Master 400-day...I ended up gluing it back in.
I'm not sure on how brittle the anchor pins are. I've heard Becker's might be. I had a bent anchor pin on a recent per WWII Kundo and I seemed to get away with simple bending while supporting the base of the pin.