Booklet Bk138 - Unseparated - This Unusual - Or Common?

UNITRADE 2014 page 514, re BK138 asks "does 138a exist? Confirmation requested).

I have two unseparated pairs of BK138 (flag) - one pair with TI and one pair without. The covers are scored but stamp panes are unseparated. Booklets have not been opened.

What do you think of this?

You must be working with a very old catalogue. This booklet is listed in the 2017 Unitrade on page 550.

When you say 'unseparated pairs' are you referring to 'two pairs' of stamps inside each of the two booklets or a 'pair' of booklets? With the inclusion of 'scoring', I believe you are saying that the stamps inside each booklet are scored but not fully perforated. If this is correct, then congratulations are in order as they are valuable to variety collectors.

This issue is listed as follows:
BK138a glued flap, no TI
BK138b open cover with TI
BK138c glued flap with TI

Hi BlackJag - there is no scoring on the stamps. In fact - oddly - each has a full (continuous) pane perforated - straight edges on outsides only. So - I can't figure how these came about.

CanadaStamp, your booklets are BK139. The description below the number in Unitrade says "rouletted to allow for separation into two booklets of 25"

It contains a pane of 50 stamps, Unitrade 1356b.

Then this is an odd product to say the least. It's two 25 stamp / $10.50 booklets joined together. How would the post office cashier ring this in? (and yes - I'm still running with UNITRADE 2014 - hoping for a new one at Xmas)