The attack sounds very similar to the typical Roland Piano samples of the early 90s (e.g. Piano 2 in the GM.DLS soundfont that ships with Windows, or from a Roland SC-55/88). There appears to be a bit of a volume and filter envelope applied to it, plus the last third or so of the waveform appears to be badly looped, so it looks like the sample was processed further and it will be difficult to achieve exactly the same sound, it will require a lot of guesswork. But depending on how close you need it to sound, taking Piano 2 from GM.DLS as a start should get you pretty far already.