Model 204 wasn't the first I used (it might have been the fifth or sixth). I was a member of a small team that wrote an interface to M204 from Unix workstations. Fun times. :-)
If I recall correctly, these were all before I used M204: datatrieve; a product that I'm not sure I can talk about; dbase II; dbase III; informix; and ingres. Quite a few others after M204.