it could in fact be a no4 mk1/2 , assuming it possible that an early LB mkI got sent in for FTR to mk2 status , the LB mkI is rarer as there were not so many made prior to changing to the mkI* ,
that might account for his insisting it to be a mk2[it would still be marked ..no4 mk1/2 ....FTR at FAZ tho]

eather way you will be happy with a longbranch from my point of view ,