I'd say 58 cm.

Most the time virtual mean the direct distance from the seatpost to the headtube on frames with a sloping toptube such as the Pilot and other compact frames.

Most 58 cm bikes have a toptube of 58 cm.

If it's referring to the seatube length, then the shorter distance will be the actual since it is a sloping totube. The vritual will be the ditance to the imaginary tube had it been straight, which would be a greater distance, more like a 58.

I could be wrong but I'm betting a 58cm bike.

Bike was sized in 50-54-58 and 63.......I can't find the geo chart for this model.

http://www.trekbikes.com/au/en/bikes/2005/archive/1000c