When ordering the optional 0.13DC, there is no change in price and there is no specific part number. If you could make a note on the order that you wish to have the optional 0.13v DC then we will make the necessary change.
For you information, in DC, 0 – 1.3V corresponds to 0 to 130dB with the weighting and time constant corresponding to the current display setting.
Please let me know if you require any further information.
Many thanks,