In 1984, LEGO released 17 Duplo sets across 3 subthemes, all of these sets have been retired. Subthemes for that year included Baby, Supplementary, and Trains.
Most valuable 1984 LEGO Duplo set
2649 Sea Explorer $120.95
Largest 1984 LEGO Duplo set
2375 Basic Set Town 53 pieces
Most owned 1984 Duplo set
2619 Helicopter
17 sets

1900 Special Trial Pack Duck

Theme Duplo
Year 1984
Pieces 6
Availability Retired
1900 LEGO Duplo Special Trial Pack Duck

2054 Squirrel Rattle

Theme / Subtheme Duplo / Baby
Year 1984
Pieces 2
Availability Retired
2054 LEGO Duplo Baby Squirrel Rattle
Value $40.88

2055 Rocking Horse

Theme / Subtheme Duplo / Baby
Year 1984
Pieces / Duplo figures 2 / 1
Availability Retired
2055 LEGO Duplo Baby Rocking Horse
Retail $15.50
Value $44.57
Growth  +187.5%
Annual growth 3.0%

2305 Red Base Plate

Theme Duplo
Year 1984
Pieces 1
Availability Retired
2305 LEGO Duplo Red Base Plate
Retail $9.99
Value $34.53
Growth  +245.6%
Annual growth 3.8%

2307 Supplementary Set

Theme / Subtheme Duplo / Supplementary
Year 1984
Pieces 18
Availability Retired
2307 LEGO Duplo Supplementary Set
Retail $9.99
Value $26.82
Growth  +168.5%
Annual growth 2.4%

2309 Supplementary Set

Theme / Subtheme Duplo / Supplementary
Year 1984
Pieces 25
Availability Retired
2309 LEGO Duplo Supplementary Set
Retail $12.99
Value $31.57
Growth  +143.0%
Annual growth 2.2%

2335 Basic Set Animal

Theme Duplo
Year 1984
Pieces 9
Availability Retired
2335 LEGO Duplo Basic Set Animal
Value $13.11

2345 Basic Set House

Theme Duplo
Year 1984
Pieces / Duplo figures 15 / 2
Availability Retired
2345 LEGO Duplo Basic Set House
Value $85.00

2355 Basic Set Vehicles

Theme Duplo
Year 1984
Pieces / Duplo figures 25 / 2
Availability Retired
2355 LEGO Duplo Basic Set Vehicles
Value $101.89

2375 Basic Set Town

Theme Duplo
Year 1984
Pieces / Duplo figures 53 / 4
Availability Retired
2375 LEGO Duplo Basic Set Town

2618 Deep Sea Diver

Theme Duplo
Year 1984
Pieces / Duplo figures 2 / 1
Availability Retired
2618 LEGO Duplo Deep Sea Diver
Value $39.94

2619 Helicopter

Theme Duplo
Year 1984
Pieces / Duplo figures 2 / 1
Availability Retired
2619 LEGO Duplo Helicopter
Retail $9.99
Value $25.85
Growth  +158.8%
Annual growth 2.3%

2636 Tow Truck

Theme Duplo
Year 1984
Pieces / Duplo figures 3 / 1
Availability Retired
2636 LEGO Duplo Tow Truck

2639 Petrol Station

Theme Duplo
Year 1984
Pieces / Duplo figures 12 / 2
Availability Retired
2639 LEGO Duplo Petrol Station
Value $98.60

2649 Sea Explorer

Theme Duplo
Year 1984
Pieces / Duplo figures 36 / 3
Availability Retired
2649 LEGO Duplo Sea Explorer
Retail $24.99
Value $120.95
Growth  +384.0%
Annual growth 3.9%

2713 Train Points

Theme / Subtheme Duplo / Trains
Year 1984
Pieces 10
Availability Retired
2713 LEGO Duplo Train Points
Retail $11.99
Value $30.71
Growth  +156.1%
Annual growth 2.3%

2717 Train Bridge

Theme / Subtheme Duplo / Trains
Year 1984
Pieces 5
Availability Retired
2717 LEGO Duplo Train Bridge
Retail $8.99
Value $38.13
Growth  +324.1%
Annual growth 4.2%