Proper - full name of builder :

Stocznia im Komuny Paryskiej Gdynia ; Poland .
Launched : 02-10-1663
Completed and handed over to Polish Ocean Lines : 31-12-1963 ;
Maiden voyage to India commenced 19-02-1964 .

Main Particulars :
General Cargo
TONNAGE :
GT 5568/8620
NT 3127/4861
DWT 9660 / 11600 t

Dimensions : 152.52 x 19.40 x 7.70 / 8.75 [m]
Cargo holds : 5 ( 5 hatches )
Propulsion : 1 HCP-Sulzer 6RD68 7200 hP ( 5300 kW )
Single screw
Speed max : 15.6 knots
Class : LRS +100A1 / (1964)PRS

Proper - full name of builder :

Stocznia im Komuny Paryskiej Gdynia ; Poland .
Launched : 02-10-1663
Completed and handed over to Polish Ocean Lines : 31-12-1963 ;
Maiden voyage to India commenced 19-02-1964 .

Main Particulars :
General Cargo
TONNAGE :
GT 5568/8620
NT 3127/4861
DWT 9660 / 11600 t

Dimensions : 152.52 x 19.40 x 7.70 / 8.75 [m]
Cargo holds : 5 ( 5 hatches )
Propulsion : 1 HCP-Sulzer 6RD68 7200 hP ( 5300 kW )
Single screw
Speed max : 15.6 knots
Class : LRS +100A1 / (1964)PRS

Rather inconspicuous "Francesco Nullo" was a prototype of a type B-41 general cargo ships, that turned out to count 23 vessels.
20 of them were built by Gdynia Shipyard, 2 in Szczecin and 1 in Gdansk. Some hulls were subcontracted in Spain and Portugal.
Altogether 13 ships were built for Poland, 5 for China, 3 for Iran, one for France and one for Albania.
Chronologically, following vessels were built (first names):

B41/1 FRANCESCO NULLO, IMO 5427112, 1963, Gdynia, for Polish Ocean Lines;
http://www.shipspotting.com/ships/ship.php?imo=5427112

B41/2 LENINO, IMO 6415180, 1964, Gdynia, for Polish Ocean Lines;
http://www.shipspotting.com/ships/ship.php?imo=6415180

Integrated funnel turned out to be not practical - new form was designed. Additional tweendeck added in Holds 2 and 3.

B41/3 TRAUGUTT, IMO 6423357, 1964, Gdynia, for Polish Ocean Lines;
http://www.shipspotting.com/ships/ship.php?imo=6423357

B41/4 STANISŁAW DUBOIS, IMO 6423333, 1965, Gdynia Shipyard, for Polish Ocean Lines;
http://www.shipspotting.com/ships/ship.php?imo=6423333

B41/5 LENINGRAD, IMO 6515241 1965, Gdynia, for Polish Ocean Lines;
http://www.shipspotting.com/ships/ship.php?imo=6515241

B41/6 ALEKSANDER ZAWADZKI, IMO 6520466, 1965, Gdynia, for Polish Ocean Lines;
http://www.shipspotting.com/ships/ship.php?imo=6520466

B41/7 JINING (also as Ji Ning) IMO 6706632, 1966, Gdynia, for China Ocean Shipping Co.;
http://www.shipspotting.com/ships/ship.php?imo=6706632

B41/8 XINGNING (also as Xing Ning) IMO 6619554, 1966, Gdynia, for China Ocean Shipping Co.;
http://www.shipspotting.com/ships/ship.php?imo=6619554

B41/H1 PIOTR DUNIN, IMO 6613237, 1966, Sevilla/Szczecin, for Polish Ocean Lines;
http://www.shipspotting.com/ships/ship.php?imo=6613237

B41/H2 JÓZEF WYBICKI, IMO 6618859, 1967 Sevilla/Szczecin, for Polish Ocean Lines (launched as SEBASTIAN KLONOWICZ);
http://www.shipspotting.com/ships/ship.php?imo=6618859

B41/D1 YONGNING (also as Yong Ning) IMO 6726785, 1967, Gdynia, for China Ocean Shipping Co.;
http://www.shipspotting.com/ships/ship.php?imo=6726785

B41/9 CHANGNING (also as Chang Ning), IMO 6711821, Gdynia, for China Ocean Shipping Co.; rebuilt for research ship;
http://www.shipspotting.com/ships/ship.php?imo=6711821

B41/D2 SMOLNY, IMO 6829862, 1968, Gdynia, for Polish Ocean Lines; ("D" stand for additional, in Polish);
http://www.shipspotting.com/ships/ship.php?imo=6829862

B41/11 GWARDIA LUDOWA, IMO 6912645, 1968, Gdynia, for Polish Ocean Lines;
http://www.shipspotting.com/ships/ship.php?imo=6912645

Modified superstructure layout:

B41/10 HAINING (also Hai Ning) IMO 6902030, 1969, Gdynia, for China Ocean Shipping Co.;
http://www.shipspotting.com/ships/ship.php?imo=6902030

Next eight vessels were built in improved form:
http://www.shipspotting.com/gallery/photo.php?lid=1907729