Thanks for the pictures, very interesting :-? !
OK, this is not obvious, & I am still guessing to some extent, but to cut story short ? I think you have a genuine early 1979 Tokai custom model, and I also think it is expensive type ie LC80 or above (probably LC100) 8) .
Right, now here is the long answer ......
First, compare your guitar to the LC100 shown in 1978 Catalogue (see my link above). There are some differences. First thing is your truss-rod cover is different ("trc"), you have the ?diamond? shape whereas 78 catalogue shows ?bell-shape? cover. But note that ?diamond? cover is seen on Love Rock Models in 1981 Catalogue. Also your tuners are different, they are all-metal ?Grover? style (1978 catalogue shows Kluson type with plastic buttons & unusual ribbed gear-housing).
From 1978 to 1979 Tokai Reborn (ie Les Paul Standard model) had model number impressed at end of Fretboard. I would also expect same number on 1979 Custom, but I see no trace of a number on your guitar? However, I have to admit that early Custom is a rare guitar, and I just don?t know if the number was ever used on the Custom models.
In 1978 catalogue, that LC100 appears to have no number on back of headstock. That?s very surprising to me, but maybe it?s just the way Tokai took the photograph? Where do you find the Serial Number on your guitar, is it impressed into back of headstock?
I also notice your guitar has binding over the fret ends. That was a feature only done on expensive models, ie LC80 & above.
But a key feature in all this is the ?split diamond inlay? on your headstock. Of course, that is an exact copy of original Gibson headstock inlay. In fact that diamond was the main feature which Gibson tried to use in 1970's to threaten Lawsuits against Japanese makers. But, if you look in Tokai catalogues you see that in 1978 the Custom is exactly like yours with correct original Split-Diamond, however, three years later in 1981 the Catalogue appears to show Custom models with completely plain headstock ie with no inlay at all!! Then in 1982 Catalogue the Custom is shown with completely different floral inlay. Finally, in 1984 it shows another form of the ?diamond? but now it?s completely different to Gibson original (a clear example is shown in catalogue marked ?early 80?s?). The 1984 diamond continued right up until 2000 when they changed the pattern yet again, to show a sort of ?Dagger & Scroll? design :-? .
Ian.
PS- I just came back from a very enjoyable few days holiday in Madrid,... very nice city 8) !