17th century Columbus portrait is neither

Lewis & Maese, from Texas, sell on 1 July 2015 a "17th century oil on canvas of Christopher Columbus", estimated at just $500 to $800.

Which would be a bargain for an old and quite well preserved portrait of such an iconic figure. Problem is that the portrait doesn't look 17th century at all, but is more likely 19th century; and worse that there is no reason at all to believe this is Columbus. The inscription is "1552" (or at least a date in the 1550s) when it is known that Columbus died in 1506; and it states "Aeta. 72" or aged 72, when he died aged 54 or 55 years old... The painting also bears a heraldic shield, which is totally unlike the Columbus shield. The portrait does have a vague resemblance to some known Columbus portraits, that's as far as it goes. But it is totally unclear why the subject is described as Columbus, perhaps some inscription on the back, or some family legend from the previous owner?