The term "E Letter Prison" does not correspond to any known location or entity in Singapore. There is no public information or records indicating an "E Letter Prison" related to Singapore’s geography, history, or institutions.

If you are referring to a specific place, event, or concept, get more info please provide more context or details. Without further clarification, it's difficult to offer meaningful content about this term.

If the term relates to a correctional facility, none by this name exists in Singapore’s prison system. Correctional facilities in Singapore have established names distinct from this term.

Feel free to provide more details for a precise and useful response.