The concept of a "Type SE" seems to be a Japanese thing: the canonical list of plug types is maintained by the International Electrotechnical Commission, and they don't recognize it.

The best source I could find, then, is this random Japanese site, which claims that Type SE is identical to the Type C, except that:

• Type SE plugs have may have a hole for a ground (earth) pin in the middle
• Type SE plugs may have slightly wider pins than Type C

On closer observation, it thus looks like "Type SE" is identical to what is usually called "Type E"! Type E, which originates from France, has the grounding pin hole and straight 4.8x19 mm pins, while Type C lacks the hole and has slightly smaller 4x19mm pins. Side by side:

Type C Type E/SE

The concept of a "Type SE" seems to be a Japanese thing: the canonical list of plug types is maintained by the International Electrotechnical Commission, and they don't recognize it.

The best source I could find, then, is this random Japanese site, which claims that Type SE is identical to the Type C, except that:

• Type SE plugs have may have a hole for a ground (earth) pin in the middle
• Type SE plugs may have slightly wider pins than Type C

On closer observation, it looks like "Type SE" is identical to what is usually called "Type E"! Type E, which originates from France, has the grounding pin hole and straight 4.8x19 mm pins, while Type C lacks the hole and has slightly smaller, tapered 4x19mm pins. Side by side:

Type C Type E/SE

The concept of a "Type SE" seems to be a Japanese thing: the canonical list of plug types is maintained by the International Electrotechnical Commission, and they don't recognize it.

The best source I could find, then, is this random Japanese site, which claims that Type SE is identical to the Type C, except that:

• Type SE plugs have may have a hole for a ground (earth) pin in the middle
• Type SE plugs may have slightly wider pins than Type C

On closer observation, it thus looks like "Type SE" is identical to what is usually called "Type E"! Type E, which originates from France, has the grounding pin hole and straight 4.8x19 mm pins, while Type C lacks the hole and has slightly smaller 4x19mm pins. Side by side:

Type C Type E/SE

The concept of a "Type SE" seems to be a Japanese thing: the canonical list of plug types is maintained by the International Electrotechnical Commission, and they don't recognize it.

The best source I could find, then, is this random Japanese site, which claims that Type SE is identical to the Type C, except that:

• Type SE plugs have may have a hole for a ground (earth) pin in the middle
• Type SE plugs may have slightly wider pins than Type C

On closer observation, it thus looks like "Type SE" is identical to what is usually called "Type E"! Type E, which originates from France, has the grounding pin hole and straight 4.8x19 mm pins, while Type C lacks the hole and has slightly smaller 4x19mm pins. Side by side:

Type C Type E/SE