After some googling I saw that Type 19 must have had various ways in which the blade connects with the guard. The most common is version A, which looks like mine, and seem to lack a metal seppa. Then there is B and C. My vague impression is that only the combat-worthy models have visible kabaki or seppa.
I don't get how seppa works: must there be a cast depression in the guard for the seppa to sit in? otherwise I do not understand how seppa on the external side of the guard can restrict movement for long unless you weld it on