The very early R20s have subtle differences to those from 1970 and later. Brake bridge is stamped ESGE Pletscher Patent, Made in Germany. Chain-stays are a different shape where they meet the BB shell. Seat tube is waisted. Seat post binder is welded on. Steering stop is an angled pressing. Black undercoat was used. This is the only BSA branded '69-type Twenty frame that I've ever seen. I like the evidence of age and use. I always do my very best to preserve original finish.