Old street signs in the city of Oxford
The oldest surviving street signs of Oxford are easy to identify, as they all have hyphens (with BLUE-BOAR-STREET having two). The sixteen signs below were photographed by David Ludlow in 2004 and probably date from the 1840s to the 1860s: fifteen of them survive today.

The images above include two old street signs in Broad Street, one at each end. The one on the east side has been repositioned on a stone pillar outside the Clarendon Building and had to be cut in half to fit, with the hyphen faintly visible but blackened out. Originally this sign was probably sited in what is now considered to be the north end of Catte Street, as until the twentieth century Broad Street stretched around the corner as far as New College Lane.

A recently lost sign
The Victorian street sign for St Giles's Terrace on the front of 36 Woodstock Road was removed in 2011/12. It can still be seen on Google StreetView in earlier years, for instance here in 2009.
Apostrophes
Apostrophes are awkward: note that the apostrophe in ST. GILES’S-TERRACE above had to be tipped sideways in order to fit comfortably on the sign. More surprisingly perhaps (given its important role in distinguishing between the colleges of QUEEN’S in Oxford and QUEENS’ in Cambridge) the apostrophe is omitted in the Victorian sign on QUEENS-LANE.
Hyphenated Oxford street names in print
The hyphen in street names was also used in handwriting and print. This extract from Jackson's Oxford Journal of 13 September 1890 gives three examples: “Holywell-street”, “Broad-street”, and “South Parks-road”:

The convention of using hyphens in print continued well into the twentieth century in some newspapers, including The Times.
Two adjacent old street signs in Oxford
The name “Walton Street“ was only introduced in about 1855, so its sign in the photograph below probably dates from that time.

Hyphenated street signs in Oxford that have been lost
Most of these early street signs with hyphens have disappeared, often because the buildings to which they were attached were demolished or refaced. The postcard below shows two old hyphenated street-signs (BRASENOSE-LANE and MARKET-STREET) that are no longer in place. These have black lettering on white backgrounds and none of this type survive: they were probably older than the above cast-iron ones that have white lettering on a black background, and may not have been so robust.
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Later street signs
The style of sign shown on the right was used during the mid-twentieth century, and this one can be more precisely dated than that as Rectory Road was only given that name in 1959.
Street-signs are now usually mounted on concrete legs on the pavement like this rather than on houses or their front walls, so that is a useful clue to their age.
In the late twentieth century Oxford City Council started to put its new stylized logo of an ox crossing a ford on the left-hand side of all street signs, and also experimented with plastic street signs, but these do not seem to have lasted long. .