the 1973 is a good choice for a Glenrothes. In Germany it costs 77 Euro.
At a tasting session I had the chance to compare it with several other bottlings of Glenrothes: 1981 OB, 1989 OB and the Unchillfiltered Collection 1990 Sherrybutt from Signatory. The 1973 was my favourite - full bodied and spicy with a satisfying sherrycharacter that you would not think it´s 27 years old, the 1981 was too shallow imho
The 1989 is OK but you will recognize its low age. Try the Signatory bottling - it´s superb, at the same cost as the 1989 OB
the better choice (37 Euro)