Question about the speed of Sea Slug Mk1

[PreMars]

In the past, most people considered Sea Slug Mk1 a subsonic missile. but I noticed that the speed of it has been modified (about Mach 1.3) on the littilewars webpage. Could anyone provide me a more detailed explanation?
For example, how do those fire reports describe it's speed?

 

[Dilandu]

In the past, most people considered Sea Slug Mk1 a subsonic missile. but I noticed that the speed of it has been modified (about Mach 1.3) on the littilewars webpage. Could anyone provide me a more detailed explanation?

According to what I know, Sea Slug Mk1 was a low supersonic missile, that could engage only subsonic targets. Many sources apparently got confused and assumed that "if missile could engage only subsonic targets, then missile itself must be subsonic".

 

[PreMars]

According to what I know, Sea Slug Mk1 was a low supersonic missile, that could engage only subsonic targets. Many sources apparently got confused and assumed that "if missile could engage only subsonic targets, then missile itself must be subsonic".

Any references?