Mr Awe wrote:
What's a suppressed field copy? Thanks!
Suppressed Field was the early way of making film copies of programmes made on video tape: it only captured them at half of the original resolution (as it only got lines 1,3,5 etc, not 2,4,etc). Sometime in 1966 (two years into Doctor Who) the improved Stored Field technique came in (which got 1,2,3, etc) took over, and new Stored Field prints were made of all the preceding episodes (as the original videotapes still existed at that point).
The original suppressed field copies were then junked. But as the stored field copies were also later junked, there's a few cases were the only surviving copies of early episodes are surviving copies of the earlier suppressed field versions that came back from countries who'd bought them very early on.