20 spoke, bladed, 18mm, Shimano branding? I'm guessing it's got about a ~25mm rim height, as well? Sounds like a WH-R500, or an equivalent thereof.
Those Shimano 'Road Sport' wheelsets have a reputation for being pretty solid, if somewhat heavier than similar offerings from Fulcrum or MAVIC.
I've put 500 miles in a single week on a set of those (running 28mm tires) and I weigh significantly more than OP.
I'm also guessing that those super narrow 32h are the old 'box section' style rims as well. In most cases, the modern 'semi-aero' profile rims are stiffer than the box-section rims, allowing them to be as 'strong' if not stronger, with fewer spokes.