It's great to see these early quartz watches still going strong, yours looks to be in fine shape Keith. There was a 1970 35 series Astron on eBay a few months ago, in fantastic condition - it even had the original strap and buckle. I dropped out fairly early due to lack of funds at that time but I think it went for over £5,000. The only person I know who owns one is Stefan Molle, a huge Seiko collector.
Thanks for taking the time to write this piece, it's great to see that these groundbreaking pieces are still appreciated