I picked up a Seneca off Craigslist a couple years ago, I started to mess with it and sacked it in an gave it to the bike mechanic at the LBS. I'd just done a couple Cunningham Nishiki builds, an Alien with Tange Prestige, and an Ariel with full 4130 frame and fork. The Seneca felt hefty but was finished nicely, lugged crown fork and clean welds. The Seneca was the middle model of the 5 bikes offered by Raleigh in 1985. Once I started pulling it apart I noticed that the steer tube is stamped "high-ten" and based on the "Raleigh Reynolds" frame tubing decal, I figured out the stays were high-tensile steel too. Hence, the 32 pound catalog weight that you found on MOMBAT's Raleigh pages. I've built probably 100 bikes in the past 10 years (for myself, family, friends, or to donate to charities... I've gotten very picky about the quality of the frame since space is an issue and I'll only take on lighter weight frames for my personal use. The mechanic at my LBS built up the Seneca, he rode it for a month and sold it. He didn't like the long top tube coupled with the long chainstays and the slack angles. The bike was good for an around town bike but not really trail worthy was his description. If you're planning a commuter build then the Seneca should make for a nice bike with a stable ride.
Good luck ! ! !