Ibanez T150S

6 ohm speakers are not common and must be specially sourced, so if Ibanez went all the trouble to get them, instead of easy off the shelf 4 or 8 ohm ones, it means your amp can NOT drive 4 ohm (which will sink to 3 ohm at some frequencies).
If they work, leave as is, Ibanez are no fools and use good parts.
If broken, replace with 6 ohm same type IF you find them, OR 8 ohm, which is safe.
 
Sorry but there´s nothing readable there.

IF you dare, unscrew it from chassis and tke a couple detailed closeups from the other board face, showing any labels there.

Although if it works fine, I wouldn´t mess with it.

Whay´s your purpose?

Increase power?

Replace speaker?