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Those look like urethane to me.

Put them on a sanding block and spin the wheels up. Youll soon know if theyre silicon or urethane.

I really can't tell just by looking at the picture, but they do look more like Ortmann or Paul Gage urethane tires. Urethane tires are fairly easy to sand compared to silicone tires, like Super Tires. Some older silicone tires like Indy Grips also sand more easily. One other way to tell is by how the tires act on a dusty track. Silicone tires will have better grip to start with, but quickly get coated with dust and loose most of their grip. Urethane tires will not have quite as much grip on a dusty track to start out with, but the will not loose as much grip as the laps pile up because dust does not stick to them.

Paul Gage does not make tires with almost square sidewalls like this. Never seen Ortmann's so can't comment on this.

They look like Super Tires (silicone or urethane) that have been rounded a bit. From the looks of it, I would guess urethane (Yellow Dog) but use the methods described to confirm.