This is a Rodan-Okaya CD14 symbol tube – it has the symbols +, −, × and ÷. It has the same form-factor as the CD11, so the digits are around 19mm. This particular tube was slightly damaged – the silver casing was loose and easily pulled off, so you get to see what this, and other similar tubes, look like ‘in the raw’. This was easily fixed.
I find this ridiculously addictive to look at!