FN introduced the HP-DA in 1983 for the XM-9 pistol trials and produced them until 1987.
In 1990, FN re-introduced them with a redesigned DA trigger in both DA/decocker and DA Only versions. FN called them the Browning BDA9 and BDAO in the US, and the FN HP-DA and HP-DAO in Europe. The DA trigger on my post 1990 FN-HP is excellent - light by DA standards. It's almost a two stage trigger with a very light pull initially with very abrupt stacking in the last 1/4 or so of the pull. However, the entire pull is very smooth over all, allowing a very quick and smooth pull when shooting at speed, or a very easy to stage pull when accuracy matters on the first shot.
The trigger reach is also quite short by DA standards, particularly when de-cocked. If your hand fits the Hi Power well, and/or you have issues reaching DA triggers, this is a DA pistol that will work well for you.
It shares the same hammer shape as the FN SFS Hi Power, which is a Mk III Hi Power with the Safety Fast Shooting system where the safety lowers the hammer onto a hammer block while leaving it cocked and locked. Unlike the SFS Hi Power, parts commonality between the FN HP-DA and the Hi Power is very low, and the pistol was also restyled externally with a Sig Sauer looking trigger guard and a more angular treatment to the front of the slide. Below is my FN SFS Hi Power made around the same time, with the same epoxy paint on top of parkerized finish. The finish won't win beauty contests on either pistol, but it is very durable and does an excellent job of preventing corrosion. My SFS was a daily carry pistol for nearly 10 years and shows very little wear.
The major downsides with the FN-HP are the unique magazine that can be hard to find and is limited to 10 rounds (the earlier 14 round magazines are very hard to find), and the 1980s style grip with the thumb rests on each side. Worse, the thumb rest on the left grip panel tends to block access to the magazine release, requiring a shift in grip to drop the magazine. Replacement grips have proven impossible to find.
Still, it's a fun pistol to shoot and is an interesting attempt at evolution/modernization of the Hi Power.