Just before the Company's demise, caused by the owner's death in the early 1970s, Portass introduced what was listed in their advertising literature as both the "D5" and "PD5". With  a 35/8" centre height and 17 inches between centres, it employed the same basic headstock, tailstock and long usefully-long 230 mm five T-slot cross slide as used on late versions of the Model S - but with a entirely new bed and carriage. 
Unlike all previous sub-Dreadnought-sized Portass lathes, tumble reverse was fitted as standard and the apron carried proper split nuts to grip the 8 t.p.i. 5/8-inch diameter leadscrew  - though there does not seem to have been a mounting bracket to carry the essential thread-dial indicator. The changewheels, guarded by a heavy, cast-iron cover (though this could be deleted, to save money) comprised: two 20t, and one each of: 25t, 30t, 35t, 40t, 45t, 50t, 55t, 60t and 65t.
With its 1-inch diameter, 5/8"-bore headstock spindle running in plain split bronze bearings, the backgeared headstock, could (at the customer's preference), be fitted with either V or flat-belt drive (the majority appear to have chosen a V belt) and both top and cross-slide (square-thread) feed-screws could be had with micrometer dials - another first for a small Portass - though to be fair these were very simple, and merely engraved on the rim of the full-circle handwheels. Another advance was the use, and not before time, of a standard-fit T-slotted cross slide that was sufficiently long (and with enough travel) for it to make effective use of a vertical milling slide - every previous type being far too short.  Production models were fitted with a much longer (1-inch diameter) tailstock barrel than that shown in the publicity pictures, though the No. 1 Morse taper centre was still inadequate for the potential work capacity of the lathe. The picture below shows the D5 as manufactured during 1964, and complete with the maker's built-on countershaft unit, an assembly adapted from a bench unit used since the 1950s for the  Model S.
On its introduction the lathe was priced at £47 : 10s : 0d for the basic machine complete with faceplate, catchplate, changewheels and centres. To this had to be added a countershaft (including belts and pulleys) at £9 : 11 : 6d, a Burned 4-inch 3-jaw chuck at £10 : 17 : 6d and a suitable motor. A 7.5% discount was offered for cash at the factory door (or "free" extended credit terms) making a total of £62 : 17 : 6d. As a comparison, in the same year, the superior Myford ML7, with the same level of equipment, was £81 : 12 : 6d - a sum some 30% more and equal to nearly half a month's salary for a newly-qualified teacher. Because the price was so competitive the lathe's fit, finish and detailing were merely acceptable, though a little cosmetic improvement was attempted by frosting the outer faces of tailstock and top slide. In its final form the price had risen to £59 : 10s : 0d for the lathe plus a countershaft - oddly reduced - at £7 : 15 : 0d
Both the changewheel bracket and tailstock barrel were crudely locked by direct-contact bolts, the result being that both could never be properly secured and had a tendency to creep from their set positions. Being able to collect your lathe directly from the factory must have had its attractions for, despite its drawbacks, the PD5 must have sold well, it being commonly encountered on the used market..