After a lifetime's work -- which included striking lucrative lands deals during the boom -- Mr Gaffney left more than €17m in his will.
But it is what Mr Gaffney instructed be done with this money that has meant the popular, but retiring, bachelor will be forever remembered in his native Malahide.
Thanks to Michael's generosity, the Fry Model Railway tourist attraction in the town will soon be on display again. The railway has been in storage since being removed in recent years from its home in Malahide Castle.
But Michael left instruction that is money be spent to secure the future of both the model railway and the local historic Casino building in Malahide.
Mr Gaffney donated €1.5m towards to the project to rehouse the railway, which was bought by Dublin Tourism in 1976 from the late Cyril Fry's widow.
It was built in the 1920s and 1930s before being overhauled in the 1980s by retired CIE craftsman Tommy Tighe to become the largest model railway in Europe. It opened to the public in Malahide Castle in 1988.
However, with the redevelopment of the castle in recent times it was planned to move the railway to Busaras in Dublin city centre -- a move which locals feared would be a major blow to local tourism.
But now the Fry Railway can be relocated to the Casino in a setting near the actual railway that serves the town. The thatched-roofed Casino was built in the late 17th century but has lain vacant since 2004.