The NTE27C256 is a 256Kbit EPROM in a 28−Lead DIP type package ideally suited for microprocessor systems requiring large programs and is organized as 32,768 by 8 bits.
The NTE27C256−12D, NTE27C256−15D, and NTE27C256−70D have a transparent lid which allows the user to expose the chip to ultraviolet light to erase the bit pattern. A new pattern can then be written to the device by following the programming procedure.
The NTE27C256−15P is suitable for applications where the content is programmed only one time and erasure is not required.
 
Full spec sheet:
https://www.nteinc.com/specs/27C/pdf/nte27c256.pdf