T-Mar, thank you so much, and apologies again for not knowing about the date letters. This is great to know and allowed me to determine more about the frame. If of use to your many readers, I found a recent website for Centurion enthusiasts here: Vintage Centurion Bicycles. Sheldon Brown's site has a contribution from one of his successors at https://www.sheldonbrown.com/centurion.html, which quotes you at length, something that will never, ever happen to me. Thanks again!