You need the serial numbers to determine age. There are a number of websites that will correlate the age of the piano with the serial number. Examples below --
Steingraeber:
https://www.dieklaviermachermeister.at/images/pianonummern_steingraeber.pdfBaldwin:
Baldwin vertical pianos up to 42” tall
1984-1343955 1989-1453070 1994-1521569 1999-1556889 2004-1573781
1985-1365505 1990-1470443 1995-1529416 2000-1563029 2005-1575074
1986-1383187 1991-1487131 1996-1536461 2001-1569711 2006-1575410
1987-1406054 1992-1501002 1997-1543640 2002-1570650 2007-1573766
1988-1430796 1993-1512277 1998-1550294 2003-1572930 2008-1577265
Baldwin vertical 248A Pro, 48”
1990-427993 1991-435212 1992-440915 1993-445623
Baldwin vertical pianos 44” tall and up: 6000, 5050, 248 (after 1993), 243
1984-387119 1989-416254 1994-450198 1999-474091 2004-485396
1985-394421 1990-424008 1995-454696 2000-477951 2005-485919
1986-401172 1991-430665 1996-459495 2001-481890 2006-486089
1987-405919 1992-431017 1997-464403 2002-483743 2007-486503
1988-412016 1993-431302 1998-469198 2003-485054 2008-486686