I ordered my AR in August of 1997...a memorable year because in Winnipeg, we had a truly epic spring flood when much of Southern Manitoba was under water. I have the paperwork somewhere, but I think my frame with Phil BB and Tange Rollerball headset, cream fill and name on top tube was 1375.00. It is Waterford-made , 753 with 531 forks....fun fact is that 753 has to be silver-brazed and Reynolds required framebuilders to pass a test because silver-brazing is less fault tolerant than brass-brazing. Waterford's builders consistently scored highly on that test and therefore were in a class by themselves. Frames took around 6 hours to build....later customs take 20+ hours to build.
Yours looks to be the same vintage as mine. I was intrigued by the AR because I already had (and still have) a 93 X0-1. The AR is plusher-riding. Garrett Lai of Bicycle Guide, when he reviewed the bike compared it to a Land Rover or a Merceded....in contrast , the X0-1 is more like a sports car.Both fun bikes
I think in 1998, the marriage with Waterford went a bit pear-shaped(Herons and Rivendells consumed a lot of set-up time compromising Waterford's own brand,IIRC) and they went to Match with Curt Goodrich among others...and started making Rivendells with other tubing; mixing Columbus, Vitus and maybe True Temper with Reynolds 725 and the buyer had a few more options