There are two types of 3400. The EU model looks very like the 1100 type and is designed to be used with a Beomaster 3400. It has the option of being fitted with a CD4 decoder and if fitted, there will be a small red light next to the nomenclature on the top panel. Most 3400s do not have this fitted. These are the Type 5703.
The waters are muddied slightly by the existence of a US only model, the Type 5726, which resembles the 2402 in shap and has a control panel fitted to the front and is much more streamlined. This model is stereo only and was designed to be used with the Beomaster 2400 though was not remote control.
I would guess you have the latter. These are very good sounding decks and, as they are simpler than the tangential models, have the advantage of reliability. However they are not that sought after so will command a relatively low price. I do not follow the US market but in the UK, £50 would be the type of price with a stylus. From a sonic view, this is a bargain.