$90.85est. delivered
The cheapest Demi here at $91 delivered, and rgbpd1 titles it works, with a fine nib. Ask when it was last filled.
Parker Vintage 51 Demi Black Fountain Pen-- works--fine point-squeeze fill
Parker · 1948–1960 · Aerometric
Parker 51 Demi Aerometric
Shorter 51, 1948 to 1960
For its first six years the 51 came in one size. In 1947 Parker added a shorter Vacumatic version, and in 1948 it gave that pen the new Aero-metric filler and called it the Slender, renaming it the Demi a couple of years later. The Vacumatic Demi had looked stubby, so Parker made the Aero-metric one a bit longer and slimmer than before. From about 1950 the Demi used a cheaper hoop filler, a U-shaped bar wrapped around the Pli-Glass sac, much like the one in the Parker 21. A 1955 pen has that filler and probably no date code, since U.S. 51s stopped carrying one in the early to mid-1950s. Parker never made a double-jewel Demi or built Demis in Britain, and it dropped the model around 1960. It writes like any 51, and it suits smaller hands and shorter pockets.
Spec at a glance
- Brand
- Parker
- Filling system
- Aerometric
- Era
- Post-war golden age
- Years made
- 1948–1960
- Made in
- Janesville, Wisconsin
- Material
- Lucite barrel and hood
- Cap
- Slip cap
- Nib grades seen
- Extra fine, Fine, Medium
- Typical eBay ask (Oct 5, 2026)
- $100–$190
What to check before you buy
The Pli-Glass sac is decades past the life Parker expected of it, so it's the part to test. The Demi and the full-size 51 get mixed up, so a listing can be the wrong size.
- 01Size: Compare the cap and barrel with a standard 51 in the photos, or ask for the capped length. The Demi is clearly shorter and a little slimmer.
- 02Filler: Look for a photo with the barrel off. A mid-1950s Demi has a U-shaped bar around the sac, with no full metal sleeve.
- 03Sac: Ask whether it fills and holds ink. Pressing the bar should draw ink in, with nothing weeping into the barrel.
- 04Hood: Check the hood in the photos. It should be free of cracks and deep scratches, with the nib centered.
- 05Cap: Look at the cap and clip in the photos. The cap should sit straight and match the shorter barrel.
Buying guide
Which one to buy
§ Oct 5, 2026Our pick is rgbpd1's black Demi, titled works with a fine nib, at $91 delivered. Only 10 are for sale, asking $100–190 delivered for most, with rgbpd1's "works" pens at the bottom and Teal and Burgundy pens at $176–215. Make sure it's really a Demi by comparing it with a full-size 51 in the photos or asking for the capped length, and ask whether the Pli-Glass sac fills and holds ink. A mid-1950s Demi usually has no date code, so don't mark one down for that.
- Listed now
- 10
- For parts
- 0
- Typical ask
- $100–$190
- Full range
- $82–$215
Cheapest 
Best value $109.25est. delivered
A gray Demi titled works, with a fine nib, near the bottom of the $100–190 band. It's from the same seller as the cheapest pen, so pick on color.
Parker 1951 Vintage 51 Demi Gray Fountain Pen works--fine--squeeze fill
View on eBay ↗: Parker 1951 Vintage 51 Demi Gray Fountain Pen works--fine--squeeze fill$109.25 est. delivered
Easiest to get working $164.00est. delivered
Titled serviced, with a 14K medium nib and a gold cap, so it should need the least work. It ships from Argentina for $25, so ask what was serviced and how long delivery takes.
PARKER "51" DEMI - Navy Gray Gold Cap - AEROMETRIC - 14k Nib: MEDIUM - SERVICED
Collector's pick $181.07est. delivered
Titled as a first-year 1948 Demi in green, at $181 delivered, inside the band. A 1948 pen shouldn't have the U-shaped hoop filler, which came in around 1950, so ask for a photo with the barrel off.
Parker 51 Aerometric 1st Year DEMI 1948 Green LUSTRALOY
View on eBay ↗: Parker 51 Aerometric 1st Year DEMI 1948 Green LUSTRALOY$181.07 est. delivered
Delivered prices include shipping as eBay quoted it to a US address on Oct 5, 2026. Many sellers charge by distance, so your total may differ. eBay shows yours before you pay.
Snapshot
For sale on eBay
8 of 10 listedChecked . Some may have sold.
Delivered prices include shipping as eBay quoted it to a US address on Oct 5, 2026. Many sellers charge by distance, so your total may differ. eBay shows yours before you pay.
- Used
- Cheapest
Parker Vintage 51 Demi Black Fountain Pen-- works--fine point-squeeze fill
$90.85est. delivered
$81.60 + $9.25 shipping
Buy It Now$81.60
Good buy
Black, titled works, with a fine nib.
Seller: rgbpd1
99.9% positive
- Used
- Best value
Parker 1951 Vintage 51 Demi Gray Fountain Pen works--fine--squeeze fill
$109.25est. delivered
$100.00 + $9.25 shipping
Buy It Now$100.00
Good buy
Gray, titled works, with a fine nib. Dated 1951 in the title.
Seller: rgbpd1
99.9% positive
- Serviced
- Easiest to get working
PARKER "51" DEMI - Navy Gray Gold Cap - AEROMETRIC - 14k Nib: MEDIUM - SERVICED
$164.00est. delivered
$139.00 + $25.00 shipping
Buy It Now$139.00
Good buy
Ships from Argentina. Titled serviced, with a 14K medium nib and gold cap.
Seller: fotoloncho
100% positive
- Used
- Collector's pick
Parker 51 Aerometric 1st Year DEMI 1948 Green LUSTRALOY
$181.07est. delivered
$175.00 + $6.07 shipping
Buy It Now$175.00
Good buy
Titled first-year 1948, in green with a Lustraloy cap.
Seller: trounder361
100% positive
UsedParker 51 Demi Gray Fountain Pen works--fine
$138.65est. delivered
$129.40 + $9.25 shipping
Buy It Now$129.40
Our take
Gray, titled works, fine nib. About $30 more than the same seller's other gray Demi.
Seller: rgbpd1
99.9% positive
UsedVintage Parker 51 Demi Fountain Pen Teal Body Gold Filled Cap, Original Stickers
$175.65est. delivered
$162.00 + $13.65 shipping
Buy It Now$162.00
Our take
Teal with a gold-filled cap. The title mentions original stickers.
Seller: axegou
100% positive
UsedVintage PARKER 51 Fountain Pen Demi Cap AEROMETRIC Burgundy Working
$211.70est. delivered
$200.00 + $11.70 shipping
Buy It Now$200.00
Offers accepted
This seller takes offers, and many sellers accept less than the asking price.
Fine if you might miss it? Send an offer first. Someone else can still buy it while you wait for a reply.
Want it for sure? Use Buy It Now.
Our take
Burgundy, titled working.
Seller: buywrightnow
100% positive
UsedVintage Parker 51 Demi Fountain Pen w/ Burgundy Barrel + Chrome Cap
$215.00delivered
$215.00 · free shipping
Buy It Now$215.00
Offers accepted
This seller takes offers, and many sellers accept less than the asking price.
Fine if you might miss it? Send an offer first. Someone else can still buy it while you wait for a reply.
Want it for sure? Use Buy It Now.
Our take
Burgundy with a chrome cap. The top ask here, with no working claim.
Seller: mr.inkpen
100% positive
Prices change daily. The live eBay search shows everything listed now, including anything new since Oct 5, 2026.
See every listing on eBay ↗eBay searchInk and cleaning kit
A pen that’s sat in a drawer for decades wants a flush before it sees ink. A bulb syringe, pen flush and a bottle of well-behaved ink cover most of it. This searches Amazon for the usual kit.
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